Chitose Is in the Ramune Bottle, Vol. 5 (manga‪)‬

“We’ve started going out.”
Saku Chitose is everybody’s hero, which is why he’s signed on to pose as Yuzuki Nanase’s fake boyfriend—to protect her from a potential stalker. But soon he realizes he might have bitten off more than he can chew as their “relationship” attracts jealousy from all sides, and a pack of bad boys starts coming after them! Using force really isn’t Saku’s style, but maybe some people just need to be taught a lesson…right?