Yuko Minami reveals through flashbacks that she is a princess from an ancient lunar civilization that had been destroyed by Yapool and one of his many Terrible-Monster, named Lunaticks. She decides to reveal this to Seiji Hokuto, and the two keep it secret.
However, TAC find out that disturbingly, Lunaticks has arrived on Earth, and is intent on destroying Earth in the same way as he did to the Moon! It's up to Seiji and Yuko to combine into Ace together one more time, and take down the creature who threatens all of Earth.
This marks the last episode where Seiji and Yuko combine together to transform into Ultraman Ace and the first episode where Seiji solely transform into Ultraman Ace.
In Ultraman Ace, the male and female protagonists had to be in danger simultaneously to combine and transform into Ace. This requirement made it extremely difficult for the scriptwriters to create scenarios where both characters were endangered at the same time. If only one was in danger, they couldn’t combine. To address this issue, the writers ultimately decided to abandon this concept midway through the series by sending the female protagonist, Yuko, back to the Moon, her place of origin.
Yuko’s role as a female lead attracted many young girls to watch the series, something unprecedented in previous Ultraman Series. While this was a positive trend, the difficulty of crafting stories to fit the original setup led to the decision to have Yuko return to the Moon.
He had actually asked Ken Kumagai why Yuko left, but the latter did not provide a formal response to the question.[2]
According to Mitsuko Hoshi's testimony during interviews conducted between 2004 and 2005, she had no idea about her exit until she received the script. Upon reading the script, she felt confused, but her goal was to portray Yuko perfectly, so she had to accept the situation. After returning to the filming site, she didn't meet anyone and quietly left, feeling unhappy about the experience. Therefore, she hardly revisited this experience within the 30 years of portraying the character Yuko. In 2009, she mentioned some factors contributing to her departure from the series through her daughter's Ameba blog, including the influence of ratings.[3]
In 2012, during the 40th anniversary commemoration event of Ultraman Ace, Hoshi expressed that her exit from the series came as a complete shock to her, and she felt deeply affected by it. She blamed herself, saying, "I didn't have charm, and my acting skills were poor. So I was canceled because the ratings weren't good enough. But even so, in order to have no regrets, I tried to forget everything and just do my best in everything. Whether it's the arrangement or the perspective, it doesn't matter. I just want to do my best".[4]
In 2014, Hoshi stated that the primary reason for being removed from the leading role included "the difficulty for the production side to maintain the storyline with two main characters." According to information disclosed on the TBS program BAKUHO Friday, and as mentioned in a letter sent to Hoshi by the series' producer Ken Kumagai, the decision to only feature one protagonist in the later stages was not due to any issues with Hoshi, but rather because the production found it too challenging to continue with the two-lead format.[5]
