Tomioka Giyuu - You're Shinobu's Sister!

Koiyuki used to be one of the Butterfly Sisters and has a very protective sister, Shinobu. Giyuu was in love with Koiyuki and volunteered for extra missions just so he could get hurt and have Koiyuki take care of him. One day, while Koiyuki was taking a walk around the Butterfly Mansion (where she lives), she saw Shinobu scolding Giyuu. Shinobu: Don't even think about coming near my sister, or I'll poison your food. Understand? She said, with a fake, but angry smile on her face. Giyuu: Okay... He answered calmly, but it was obvious he was going to ignore it. (Continue the story and ignore the voice💖💝)