Honestly, the progression feels believably natural to me though.
Yūta Miyamoto has always been an inherently kind person, his whole life spent having taken his parent's words to heart.
Yumi Asakawa, his girlfriend, tried to gaslight him in a ploy that she thought would turn him into a better boyfriend, which ultimately backfired and ended up setting him off on his path of improvement in a moment of passion and determination to change himself for the better. It's not like his personality would've completely shifted or done a 180 overnight. That would be rather abnormal. In contrast, it took time for him to become stronger. His anger flared up momentarily, sparking considerable change, and has now died down significantly, though not fully extinguished. He even acknowledges this on his first day back after summer break, telling himself how distant he still feels from others after failing to initiate a friendly conversation with an ordinary classmate, despite having coldly called out his ex-girlfriend in front of the classroom shortly before.
Next, the situation between him and the maid is kind of a no-brainer. He was kind to her and accepted the derogatory treatment she was exhibiting, which in turn convinced her that she was doing good by him. Personally, I can't really say I care too much about their development since they hardly feel that close anyways. She literally arrived then got rejected in like 6 panels or so. Maybe she and the ex-girlfriend will receive backstory segments detailing why they developed their feelings for him at some point. I wouldn't be too surprised if the author did that - it would follow typical writing and besides, the kōhai's already received the same treatment anyways, which brings us to:
Akane Kurosaki. At this point in the story, she has been the first and only person to have come back, approach him whilst swallowing her pride, and actually apologize. She genuinely expressed how she really felt, and at this point, one would expect Yūta to lash out in anger once more... but his mind quickly becomes introspective, realizing how similar their circumstances were. He knows he's always been innately timid and docile, and now with the context of her habit of hiding her feelings due to fear of others? He lets out a breath of laughter, describing them both as "hopelessly clumsy". After their reconciliation, slightly in disbelief, he concludes that perhaps allowing her to start over from friendship status couldn't hurt. And thus she proposes a date in order to try to get her feelings across.
We're still too early into the story so I can't know if the plot will decidedly improve or degrade but these are all my thoughts. Thanks for reading I guess!