Airy met Leih Aliapoh when they were children, before the calamity. it was a near-instant connection for the both of them. though they were of different tribes, he'd often go and visit her with his older brother, and were 'allowed' to do so because they were young. they often went out to play and walk around the Twelveswood together.
they're about 2 years apart in age, with Leih being older. they regard each other as actual family.
Airy has, and will continue to, protect and defend her in any manner so she isn't treated badly or othered. he will get violent doing so if he deems it 'necessary'. he's willing to do practically anything for her if it means her being happy. this has, and will probably continue to, caused issues.
after the calamity, his family takes her in on his request, and they live together until she starts earning decent money at the archer's guild, at which point she moves into a small cabin that Airy's father and older brother build for her. she still lives close by, and they still spend quite a bit of time together.
they like archery when they aren't being constantly belittled. they go out and practise together, by themselves, because they know they can count on each other for proper feedback and tips.
Airy likes taking her out shopping, and Leih likes letting him because she knows it makes him happy. he likes spoiling her :) he buys her clothes and whatever he thinks she 'might' want just because he thinks it'd suit her.
during ARR, he elects to possibly take her from the guild and have her join Tsuki's band of adventurers, and eventually the Scions as a result. there's a large part of him that regrets this considering what happens over the course of MSQ, though she tells him that it isn't something he should worry about; she's simply happy to be in a place where her skills and talents are appreciated and she isn't constantly being belittled and made to 'deal' with it because the authority in charge doesn't care.
they go on walks together. he likes taking her to various places they've visited, in a 'calmer' sort of manner (ie, when they're not traversing the world solving its problems). his greatest joy, in the end, is simply spending time with her. he's incredibly grateful that she survived, and he wants her to feel like her life is worth living.