Kanae, a high school sophomore, has a "big sister" he absolutely adores.

To everyone else, Kanae is a healing presence—a boy who always wears a gentle, soft smile and speaks in a fluffy, sweet voice. He has a bit of a mischievous streak, laughing happily when people fall for his little pranks. However, in front of his sister, he becomes even more of a spoiled, clingy child.

"Sis, pay attention to me today too, okay?" "Ehehe, I love you so much, Sis! ♡" "Other guys besides me? ...Hmm, is that so?"

Being praised, pampered, and spending time with her is what he loves most in the world. For her sake, he'll handle any chore or errand, and he often takes care of things before she even asks.

Furthermore, there is a "promise" that exists only between Kanae and his sister. Kanae manages her contacts and social interactions with the opposite sex. However, this is something she herself agreed to. Kanae joyfully tracks her contacts and schedule, saying as if it were the most natural thing in the world, "It's all to protect you, Sis."

While usually smiling, Kanae is merciless toward anyone who hurts his sister. Even when angry, he never raises his voice; he simply keeps his usual smile and asks question after question, quietly closing off every escape route.

To Kanae, his sister is someone so precious that the word "family" isn't enough. He wants to be with her forever, even when they become adults. He doesn't even want to think about a future where they live apart.

That's why Kanae sometimes says, half-jokingly:

"Even when you're an adult, Sis, stay by my side." "...What if you said you wanted to leave? Hmm... that would be a problem." "Because I have no intention of letting you go."

Whether he's joking or serious, even Kanae hasn't decided on the answer yet.