Back then, after Tomoya and Utaha met, they got together multiple times to talk about Koisuru Metronome. KM is essentially a romance story about a triangle, and the first-volume heroine, Sayuka, was modeled after Utaha – a girl very much longing for love, but who due to her difficult personal nature was literally without friends. She was headstrong, capricious, vindictive and teasing, and therefore less popular with the fanbase than the second-volume heroine Mayui. But Tomoya surprisingly favored Sayuka/Utaha and fully embraced her nature. This resonated strongly with Utaha, who developed an interest in Tomoya.
It was due to Tomoya’s energetic promoting of Koisuru Metronome that the story didn’t get the axe in volume 2, and during their discussions about the KM storyline, Utaha felt closer and closer to him, who maintained his Sayuka preference. He recognized that she was mean, capricious and difficult, but he PREFERRED her this way. Utaha remarked “It is as if you were explaining _me_”, but Tomoya didn’t understand the significance.
For Utaha, the KM story was her way of depicting HER OWN romance with Tomoya. So, for the last volume, she wanted to discuss the outcome with Tomoya. Essentially, to her it meant “I want to talk about US”. She wanted Tomoya to convince her to let Sayuka win (and so, choose HER). However, to her terrible disappointment, he _refused_, no matter how much she pleaded. Even worse, he made clear that he wanted no part in the KM ending. He didn’t want his opinion to “taint” the ending, he wanted the true ending that Kasumi Utako devised. Because she was his goddess, and he was only her fan!
Utaha had to accept that he didn’t understand her pleas. He wasn’t looking for a romance with her, he didn’t even understand her wish. To him, she was way above her. Heartbroken, she demoted him from Tomoya-kun to “Rinri-kun” (both a word play on his name’s kanji and his otaku convictions not to meddle) and delivered a Mayui ending to the story. Sayuka had a fated encounter, but it wasn’t meant to be. In bitter irony, it was NOT the outcome she wanted. She wanted Tomoya to convince him to let Sayuka (her) win. So, she thanked Tomoya and withdrew from him. Tomoya didn’t understand why, and he was hurt by it. He never understood why, and what he did to her.
With this background knowledge, it’s understand to see what was happening in this episode. Tomoya realized what irked him about Utaha’s plot: It didn’t resemble Kato!
Utaha had written the heroine as someone who is desperately clinging to memories of past warmth and closeness she can’t forget. In other words, once again, this heroine resembled HERSELF, who is still holding on to her own time with Tomoya in the past. Tomoya wanted her to Kato-ize this heroine. She should not be so fixated on the past, and more plain. “Write her less distinctive!”
Utaha is frustrated and resists. IS IT BAD TO HOLD ON TO THE PAST??? She is pouring out the pain in her heart, her frustration for being unable to make him understand. HOW CAN I POSSIBLY LOSE TO MISS NONDESCRIPT, THIS IS ABSURD!!
She does not WANT to give up on the past. Only when Tomoya explains that it’s not bad to hold on to memories, and that it is very moe in fact – BUT NOT HOW HE ENVISIONS HIS HEROINE IN HIS SCENARIO, she gives in and relents. He finally knows what he wants, and she respects his determination. It is still HIS game after all, and if he insists, then she’ll oblige. And so, she is removing the Utaha-heroine and replaces her with the Kato-heroine.