Plot

Ron's parents adopt a baby, and Kim and Ron are summoned to Japan to stop Lord Monkey Fist from acquiring an ancient weapon.

For health class, Ron has to take care of a sack of flour as if it were a baby, which proves difficult for him. Ron also finds out that his parents have adopted a baby girl, whom he immediately resents, referring to her as "the intruder." Also, Kim and Ron find out that Lord Monkey Fist has stolen a scroll containing instructions which could enable him to acquire a powerful ancient weapon. When they travel to Japan to stop Monkey Fist, Kim is concerned about Ron being reunited with Yori, the student ninja who was once romantically interested in Ron.—Joshua Kreitzer

Ron must take care of a flour sack for his health class assignment, but his responsibilities become more complicated when he becomes an adopted brother of a baby girl. Ron becomes jealous of his adopted sister, when he tries to take care of a flour sack, he ends up going through a series of mishaps. Ron purchases all of the flour sacks at Smarty Mart so he can pass his assignment. At the same time, Kim and Ron must help Yori when Monkey Fist plans on finding a secret weapon. Ron is struggling to tell Yori about his relationship with Kim, but she assures Ron that she is supportive of his relationship. Team Possible tries to intercept Monkey Fist at the second shrine, but they are defeated. Ron must babysit Hana and he tries to take care of his flour sack. Kim goes with Yori to protect the third shrine, but the two are captured by Monkey Fist and his minions, he forces Kim and Yori to get the final key. Kim asks Yori if she is okay about her relationship with Ron, she reveals Kim that Ron is her destiny, both of the girls retrieve the final key. Ron arrives to save Kim and Yori from the monkey villain. Hana defeats Monkey Fist by using her strength, with the shrines compromised, Yori leaves the keys in Ron's protection and he begins to accept Hana as part of his family. At health class, Jim and Tim reveal to Ron that they know that he has purchased all of the flour sacks at Smarty Mart, Ron tries to deny it, but he gets a failing grade from Mr. Barkin for trying to take a shortcut in order to pass. During the credits, Ron plays with Hana at the playground, he notices his female classmate playing with her flour sack at the swing set. Ron and Hana look on in disturbance and he takes his adopted sister to the slide.—dawsonpersi