Brand New School Day

Brand New School Day (ぶらんにゅーSCHOOL DAY) is a one-shot manga chapter by Yasuhiro Kano. It was serialized in Weekly Shonen Jump.

Plot
Shinjou wants to enter high school as a new man, since he had not been very popular back in Middle School. As he's trying to edge his way into society with his new look and personality, he happens to bump into Kurai Kako, a classmate from Middle School who had been just as invisible as he was. With her new look and personality, has arrived for just the same reason he has, and she's looking forward to snagging a boyfriend for high school. They'll just have to make a bet -- who'll get a boyfriend/girlfriend first?