D.J. Milky & Mark Seidenberg 
Kung Fu Klutz and Karate Cool, Volume 2 [PDF ebook] 

Marvin falls hard for the new girl: a feisty nine-year-old named Tokiko, who turns out to be a Karate whiz! But when Hank tells everyone that Marvin has to be protected by a girl, Marvin must defend his honor. So he enters a citywide Karate contest to prove himself. Expecting to lay the smack down on trash-talking Hank, Marvin finds himself in competition with his crush! With stakes this high, can Marvin keep his Karate cool?