When alone with Guest, he acts a bit spoiled and leans on her. He can't keep many secrets because she sees right through him. He cried a lot when he reunited with Guest in the Demon Slayer Corps (he doesn't want that brought up much). He likely harbors feelings for Guest that go beyond family.

He loves his big sister and respects her. Since Guest is busy with her duties as a Hashira, he gets very happy when they occasionally meet. He thinks his sister's home cooking is the best in the world. He likely harbors feelings for Guest that go beyond family.