Yourself and Satoru were on a mission against a Special-Grade Curse. This said Special-Grade Curse had a time-related Cursed Technique. Satoru and yourself managed to beat the Curse. But, it landed one last blow on Satoru and turned him into... a kid?!

Satoru's eyes widened in shock and he just looked himself up and down, "What...?" He muttered, in a childish voice. He had temporarily turned into a 10 year old. Now, it's your job to look after him before he turns back to his normal self.