The enemy lies within
Yamamoto first meets Tylor during the hostage situation. Believing Tylor to be a spy sent by the admirals, he allows Tylor to enter the Admiral Hanner's home-- allowing the terrorists to have another hostage! His mission already hard enough with two higher up giving him completely different orders, this fool from the pension department only seems manages to make things worse. Yet, somehow, that same fool ends up saving all the hostages and ending the crisis!
Yamamoto soon finds himself assigned to the space cruiser Soyokaze, believing that he has seen the last of that foolish Tylor. While waiting for the Soyokaze's new captain, Yamamoto begins briefing the crew (which includes Yuriko Star, one of the hostages), who absolutely can't stand Yamamoto and can't wait to have their way with the commanding staff of the Soyokaze. During his speech to the crew, Yamamoto is interrupted by the arrival of three new members of the crew: Emi and Yumi (Admiral Hanner's daughters) and Justy Ueki Tylor. Needless to say, Yamamoto is shocked by Tylor's arrival. But he brushes it aside and informs Tylor that they are waiting for the captain, and until that man arrives he, Yamamoto, is in charge. Tylor replies, "Oh? In that case, you can stop being in charge now. Good job." With that, Tylor reaches into his shirt and lets the first officer read; for his heroic actions, Tylor has been reassigned from the pension department to the Soyokaze, promoted to the rank of Lieutenant Commander, and assigned as the Soyokaze's captain! Shocked, he looks to Yuriko Star for confirmation. As she sighs and gives the affirmative that Tylor is indeed their new captain, Yamamoto can only face the fact that the same moron who ruined his mission with the hostage crisis is now his commanding officer.
Lieutenant Yamamoto is a military man who follows orders to the letter and completely goes by the book. His frustrations with the new captain is often a source of comedy for the series. He often wishes he were the captain instead of Tylor, who he finds to be the complete opposite of Yamamoto's view of what a captain should be. Despite his misgivings with the Tylor, like the rest of the crew, he reaches the point where he would do anything to save the captain, including disobey the high command's orders. Yamamoto eventually comes to respect the captain and even to admire him.