The Underestimated Waterboy (Naruto Fanfic)

Ruthless, Cold, Serious, Heartless that's what Mizuko used to be until he ran away from his home and bumped into Kakashi where he was taken to the hidden leaf village now his a playful and caring kid who would do anything to protect his village and comrades

But because of his training, his skill level is higher than an average Chunin even still a lot of other ninjas underestimate him. and that's when he shows his true powers