This is apparently the final chapter of Nakahira's Sakura Ganbaru! manga series:
In an effort to get one last match with her rival Sakura, Karin turns the entire class' graduation ceremony into a combat ring. But at the end, instead of discouraged her, the fight inspires Sakura to become a teacher (which plays into the epilogue of the original Sakura Ganbaru! manga which depicted an older Sakura in the role of a PE teacher).