User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-16281343-20141120032411/@comment-1359322-20141120045615

Well it's probably for there to be more character development for Yuuto. Yuuto's character has been kinda deadpan for a while already, maybe Ishibumi thought that inserting Tosuka would revive his character and help boost Tsubaki's character at the same time.

What i hope doesn't happen is that Tosuka is actually dying and just came to give Yuuto a power-up. Then again, it might be interesting if that happens. Yuuto gets a power-up and Tosuka's death might help strengthen Tsubaki's determination, character development for both. Though it'll be sad if that happens. Mix emotion on my own theory. >___>