Aina is a first year at Oumi Women's University. She joins Grand Blue Diving Club after getting to know Iori and Kouhei. She is a really shy girl and hates having to expose her skin. She soon becomes good friends with Chisa.

She used to wear strong makeups to appear attractive not realizing her very makeup was a turn-off for men. She was part of the Tinkerbell Tennis Club but she was always looked down upon and made fun of by her seniors. Iori and Kouhei came to her rescue when she had it enough during the Miss Izu Contest as she resorted to getting drunk and broke down in tears in front of them.
Iori's words after saving Aina from the depth of despair during the Miss Izu Contest moved her so much so that suddenly her heart skipped a beat for him. She soon finds herself having feelings for Iori but she has been keeping her feelings to herself and she is yet to tell Iori how she feels about him. Iori is also the reason why she approached Azusa to let her join Grand Blue Diving Club.