Please forgive Sensei's mistakes in the past. Those were her mistakes before she gained enlightenment. If you remember correctly, she came to Reiji's house with good intentions, acting like Yuko's daughter, etc. When she saved Reiji's brother, that was genuine without ulterior motives. She also saved Gen's father. Now, she's actually prepared to say goodbye for good. Unexpectedly, Reiji accepted her feelings, surely wavering her, and she had her hopes back.
It had to take Yuko saying the magic words:
Reiji is in Tokyo with Nagi Aoe and Chako's mom storming into the Kuroses to accidentally confirm what Yuko said to make Yuri dive headfirst into her abyss once again.
And her dismantling the family and saving Gen's dad's life, even though they were nice actions, in the end, they all worked in Yuri's favor. By leaving Reiji alone, he would have no choices, but to crawl back to Yuri for
help.
Another thing: if Reiji rejected her by saying the same argument he used with Gen (not specifying the girl, but expressing his intention), that would have only hastened Yuri's inminent flipout in another way. But at this point, i'm unsure what would have been the least bloody outcome: if Yuri kidnapping Reiji or her finding him with Nagi. In both cases, she would have become the top priority target for Ishibashi.
Whatever, Reiji
accepting Yuri has basically the same weight Nagi's nonchalance about doing JAVs has: zero, basically dead-end decisions just made because there was nothing more to lose for them and they were resigned to their fates, and not because they actually wanted to do that.
Although in Reiji's favor, him saying what Yuri wanted to hear helped him to realize what Yuko hates, because the same shit started to happen with him since he found out Yuko wasn't dead and Nagi couldn't answer his calls because of you know. Just hope Kazumasa's letter also has encouraging words for Yuri that makes her finally give up on Reiji. Remember he went there to find out his biological family, and if he succeeds... and if Reiji is decided to amend his mistakes, even if he has to take another stab, Yuri will have the best pretense to run away from the town. Japan has prefectural laws (and national laws are just minimum basis for insular prefectures without justice authonomy), so everything Yuri does in The Town, stays in the prefecture The Town is placed into. If she runs to Hiroshima (the place where NEETbro is), she will be safe as long as she doesn't come back to The Town.
Maybe Yuko, once she wakes up, and if she wakes up, that's it, should run too, because she will face some years in jail.