What is "happy!"

is a sports manga written and illustrated by Naoki Urasawa. It was published in Big Comic Spirits from 1993 till 1999. The story is about a teenage heroine who embarks on a career as a professional tennis player to repay an enormous debt incurred by her brother to Yakuza loan sharks, with the threat that if she fails, they will force her into a life of prostitution at a soapland.