Wild Strawberry

Although not related by blood, Kingo and Kayano have grown up together in an orphanage and are the closest thing either of them has to a family. When it seems that their dreams of being adopted are about to come true, their new parents turn out to be Jinka! Just as Kingo is about to be eaten, a Jinka blooms in Kayano...but her Jinka is very different. It doesn't attempt to hurt Kingo or other humans. Kingo must do everything he can to keep his sister's affliction a secret so she doesn't get pruned. One day, while working as a lowly grunt for the Flower Funeral Forces, Kingo gets an alert about a Jinka near his apartment. He rushes to the scene to find Kayano surrounded, and earns himself a bullet through the head for trying to save her. But when he wakes up, he's in a mysterious pruning facility, his sister is gone, and he is now infected by a Jinka himself—Kayano.

(Source: VIZ Media)