Slime-san to Yuusha KenkyuubuSlime-san and the Brave Research Department; Slime-san and the Hero Research Club; Suraimu-san to Yuusha Kenkyuubu; Слизь-сан и Клуб отважных исследователей; คุณสไลม์กับชมรมวิจัยผู้กล้า; スライムさんと勇者研究部

From DrCoke at MangaHelpers: 2000 years ago, there was a battle between a warrior and the demon king. Through this epic battle, the demon king won. Now, there are kids between the ages of 12 through 18 that are direct descendants of the demon king. They each have unique transformation powers that allow them to turn themselves into varying monsters, such as slimes and golems. Imaichi Butsuko and Hinase Suiren are both one of these monster kids. With the impending resurrection of the warrior, these kids enjoy their daily school lives while preparing for battle!