MY BROTHER'S FRIEND

Nanase, a polite, a little old-fashioned girl, got a boyfriend for the first time. He, a pure and kind guy, is a good friend of her brother. However, both of them have no idea what they should do next... For Nanase, holding hand would be too embarrassing, and 'date' is something mature people would do. — Description from AniList community (anilist.co).