Aishia

Aishia is Rio's contract spirit as well as a high rank spirit, of which their existence are incredibly rare. She has been contracted with Rio since the start of the novel, during the time Haruto's memories awakened within Rio.

Aishia was the one who taught Rio the Spirit Arts before he sets foot on Seirei no Tami after he fled from the Strahl region due to being framed for the cliff incident.

Prior to her awakening in her humanoid spirit form, Aishia spent the 3 preludes arc mostly by sleeping and residing within Rio. Rio would occasionally hear Aishia's voice briefly in a form of inner-monologue, where she tries to help and guide him out of his predicament. Aishia would eventually manifest herself and wakes up next to Rio on his bed after Rio successfully rescued Miharu, Aki and Masato from the slave traders.

Appearance
Aishia is stated many times in the story as the most beautiful female in the series. She has a very divine look as said by Rio seeming almost artificial in a way, her beauty leaving a cold and fleeting impression. Aishia has extremely long peach-colored hair reaching down her knee and gem-like eyes of the same color.

Personality
Aishia is a caring and curious girl. She is devoted to Rio and will always accept him. She always wants to try living the same as humans do, eating good food, taking a bath, and wearing a cute dress. Though she's pretty blunt with her words, she has a weak expression, almost expressionless most of the time, and she speaks in a monotone intonation.

According to Dryas, it's unnatural for Aishia to show a lack of expression as a spirit's personality should mature and upon becoming a high-class humanoid spirit, they should already have a full personality. Yet, although already a humanoid spirit, Aishia is like a Medium-Class spirit mentally, that is unless, being  an expressionless character is indeed her personality. Also, when she manifested, she had no memories aside from knowing all about Rio.

Pre-Awakening
Aishia first appear in Rio dream at the day Haruto memory awaken in him, she told Rio about his ability to use Spirit art, then later in the day of the Hero summoning, Aishia notifies Rio using telepathy of Miharu’s arrival and tells him to head to where she will be landing to save her from being enslaved.

Awakening
Aishia truly awakens 3-4 days after the hero summoning, appearing naked in Rio’s bed, witnessed by Miharu and Celia. After explaining the circumstance to Miharu and Celia, Rio gives her a name, Aishia, and then they start living in rock house with Aishia helping Rio teach the three of them the Japanese Strahl language.

Raid of Amande
To congratulate them on learning the Strahl language, Rio took everyone to Amande to go shopping, later going with Masato to buy sword. Aishia, along with the rest of the girls go shopping for dresses, though with Miharu, Aishia, and Celia all in one place, they soon garner a lot of attention. Afterward, Rio takes them to lunch in a high class restaurant.

In the middle of lunch, the group is disturbed by the intruding Stead and Alphonse that wish to use their table. Upon seeing the girl's beauty, the two tried to pick them up, especially Alphonse, who tries to kiss Aishia’s hand only for Aishia to swat him away. Rio tries to force them out, not caring for his attitude, Alphonse and Stead tried to use Noble strike, only for Rio to bisect their sword cleanly in half, and Aria arrive and arrest them afterward.

In the next day, Rio went to Liselotte mansion to deal with the aftermath while the rest stay in the rock house guarded by Aishia, soon, the Raid happen and monster attack the city, half of all the monsters are directed to attack the rock house, Aishia protect the house defeating many monsters with Celia's support, until they soon getting outnumbered, Aishia sent a big magic light attack to the sky as a signal, soon Rio return, and face off the monster tamer mastermind that keep watching from afar the attack to the rock house, though they manage to escape using black wyvern.

Galwark Ball
Aishia stays with Celia, Miharu, Aki and Masato while Rio attending the party, at first, they stay in the rock house, and after Satsuki visit them, they move and stay in a high class inn near the palace.

Reunion
After Takahisa ask to meet the three, Rio use telepathy for Aishia to ask them what they want, in the next day, Aishia stays to protect and accompany Celia in the inn while Rio still dealing with the letter mess

Princess Escape
After Rio decide to help Christina escape, Aishia help create a diversion by disguising her self as Christina and break through the northern gate while the rest slip through the south gate, afterward, Aishia stay with the group in spirit form with Celia while Rio bought the supply needed.

Later in the next city, Aishia offer to gather information and lurk and listening to Rio pursuer conversation, picking up their background and goal, and relationship with Lucius.

In the ambush near the border, Aishia first staying with Celia before forced to separate to face Reiss that trying to keep Aishia away from Charles group that waiting for Christina group in the way ahead, Reiss cover himself with veil of darkness where bunch of monster like revenant and minotaur jump out, Aishia easily deal with them, Reiss then taking out bunch of skeleton that after getting destroyed by Aishia, combined into one giant skeleton, Reiss escape when Aishia dealing with the giant skeleton.

Celia Escort
While Rio travel north to Proxia in order to look for Lucius track, Aishia offer herself to stay and protect Celia back in Rodania, she stays in spirit mode to save on mana expenditure, Rio also give Celia a spirit stone charged full of his mana as back up if Aishia need it.

on later days after Rio left, Celia had a tea party with Christina and Roana, and the topic start moving to Rodania noble trying to bind Rio to Restoration by engaging him with a Restoration noble girl, something that Christina and Celia believe will be impossible, Christina tell Celia, if there's a noble lady of Beltram that has a chance, its only her, Surprising her, and start making many excuses.

Later, Aishia ask Celia directly if she didn't want to marry Rio, Celia again start making excuse but it's impossible to lie to Aishia that connected spiritually, Celia then make Aishia promises to keep that conversation as secret from Rio

Later on, Aishia notice that Rio come back, congratulate him for achieving his goal, Rio ask Aishia if there's anything happening which Aishia answer there's nothing worth mentioning happen around Celia, which Rio chuckled hearing it, considering Restoration should be still in grieving for Flora missing in dragon attack, meaning Aishia doesn't consider that as important.

After Rio reach his mansion and leave Celia to attend to Flora, Aishia materialize welcoming Rio back home, after both of them exchange info about current situation, Aishia keep the marriage topic secret as promises and tell Rio that Celia wishes for a bathroom in the mansion instead.

After Rio finishes the Bathroom, somehow Celia manages to invite Rio to get in together, flustered both, Rio try to decline when Aishia pop out and tell the two she wants to get in too, later they get in together where Rio and Celia got really embarrassed with each other while Aishia doesn't care and get in without wearing anything, start washing her hair, and sleep in the bathtub.

Spirit Village
After the bathroom finished, Haruto left Rodania with Aishia for Seirei no Tami, promising Celia to come back in a month at most.

Pre-Awakening
Aishia first appear in Rio dream at the day Haruto memory awaken in him, she told Rio about his ability to use Spirit art, then later in the day of Hero summoning, Aishia notify Rio using telepathy about Miharu arrival and told him to head where she lands to safe her from being enslaved.

Awakening
The sign of Aishia awakening happen at the same time of the hero summoning where Rio sense a warm magical build up inside him, Aishia truly awaken in the next morning, appearing naked in Rio bed, witnessed by Miharu, after explaining the circumstance to Miharu, Rio gives her name, Aishia, and then they start living in rock house with Aishia helping Rio teaching the 3 Japanese Strahl language.

Spirit-folk Village
Aishia first visits Spirit Folk Village, when Rio went to the village for dropping Miharu, Masato and Aki in their protection. There she meets Latifa and Spirit Folk trio for the first time. They all get infatuated with her otherworldly beauty as well as her strong spirit aura. Latifa manages to muster her courage and asks her name. When Latifa asks her can she call her by her name, she allows her. But Spirit folk trio chooses not to call her by her name instead they choose to call her Aishia-sama, as humanoid spirits are worshipped in Spirit Folk Village. She seemed confused when everyone in the spirit folk village looks at her with reverence. There she meets her fellow humanoid spirit Dryas for the first time. When asked which all elements she can use, she replies she can use all the elements that Rio can use, at this answer all the elders and Dryas gets surprised as it is not possible for the high-ranking spirits to use all the elements as Dryas herself can only use water, air and earth.

The elders and Dryas think that Aishia is not some ordinary spirit because even the previous six high ranking spirits were not able to use all the elements. Dryas thinks in a straight up fight, she will lose against Aishia. When Rio told Dryas Aishia does not have any memories before her awakening, she then takes Aishia to her cave in the Great Tree to teach her about all the skills that spirits can use like telepathy. Thus, she spent quite a lot of time with Dryas when she was in village.

After a few days, she left the village to travel with Rio towards Strahl Region where Celia was.

Wedding Crasher
Aishia helped Rio in gathering info about how and why Celia is getting married to Charles Albor. Before the abduction Aishia used telepathy to inform Celia about Rio's presence among the crowd. When Rio was distracting the soldiers, Aishia took Celia outside of the capital and thus helped Rio in rescuing Celia from her unwanted marriage.

Amande's Trouble
Aishia notified Rio about the monster attack on Amande. Also when Rio decided to chase Lucius, she along with Celia protected Liselotte and others from revenants who had invaded her mansio. She successfully repelled all monsters and even went on to kill Alphonse who had become a black skined revenant.

Galarc Ball
Aishia travelled with Rio and Miharu in her spirit form, She acted as the messenger between Rio and the rock house group. After Rio, Miharu and Satsuki met Takahisa she went to Rockhouse to inform Aki and Masato about takahisa's whereabouts and also to inform that Satsuki would be visiting rockhouse later. She also played a fundamental role in Miharu's rescue and she also helped Miharu in conveying her feelings to Rio.

Abilities
Spirit Art: As a high-class spirit, Aishia is the pinnacle of spirit art, moreover, she also a universal attribute spirit, meaning that she can use all attribute in their strongest state.

Martial Art: Aishia possesses the same martial art with Rio through some kind of imitating ability.

Telepathy: By creating a path that connects their soul, Aishia can communicate with the one connected with her telepathically, while her main path is her contract with Rio, she also can create a temporary path when getting separated from Rio, her telepathy range can encompass an entire city.

Dream Creator: Aishia can create a dream and show it to someone that's sleeping, it can range from good dream to bad dream and the one that experiencing it can only follow the dream without any ability to change anything in it.

Trivia

 * Aishia name comes from the Spirit people language that means a warm Spring and A Beautiful Spring, with the latter meaning sharing the same meaning with Miharu name.
 * In the anime version, Aishia started to show her physical body when Rio was in the Spirit Folk Village before Rio went to Strahl Kingdom. They even had a little power contest to see her strength.