Prison School, Vol. 11 by Akira Hiramoto

The Shoulder Wars competition between the Shadow Student Council and the Official Student Council begins, and whichever side loses must disband! Vastly outnumbered, Mari knows their odds of winning are long, even with a partially resurrected Meiko to bolster their forces. To save the Shadow Student Council (and his date with Chiyo), Kiyoshi must rise to the occasion, fighting the army Kate has amassed...by going full mast!