Master Mogo-San requests that Splinter meet him at Pier 17, where he will be arriving later that same day. Mogo-San explains that he has arrived to pass on the sacred white belt of the Mogo clan to his grandson Yoku and that he needs Splinter's help in locating him.
At Pier 17, Mogo-San arrives and is surprised to find Hamato Yoshi is now a rat. Splinter promises to explain it all, but first he wants to know what brings his sensei to America.
Mogo-San explains that he has arrived to pass on the sacred white belt of the Mogo clan to his grandson Yoku and that he needs Splinter's help in locating him.
Splinter takes Mogo-San back to the sewer-lair and introduces him to the Turtles, who are most eager to accommodate him. But alas, Mogo-san learns Yoku is the leader of a criminal gang and is very distressed to learn of the dishonor Yoku bears upon the family name. The Turtles than help Splinter search for Mogo-San's grandson.
Yoku is taken prisoner and delivered back to the lair, and to his grandfather. Mogo-San shares his disappointment with Yoku and asks Splinter to burn the sacred White Belt -- better for it to be consumed by flames than dishonored by Yoku.
It seems that Yoku is a secret government agent assigned to infiltrate the Black Heart gang in an effort to gather evidence against them and flush out their leader. The Turtles are able to deliver Yoku to Pier 17 before Mogo-San's boat departs so that he can tell his grandfather the truth.
Mogo-San is indeed relieved to learn that Yoku is an honorable man, but saddened that he can no longer pass on the sacred White Belt. Splinter then reveals that he had never destroyed it.