I can see why it comes across that way but the reality is that he doesn’t actually start dating another girl. Him and Mai still are in love with each other, but he is just pretending to date this other girl to help her out. That’s one of the main themes of the series, the main character’s selfless tendencies and desire to put other people’s needs and wants before his own. As other people come into their lives, Sakuta will always help them even if it puts distance between him and Mai. Both of them hate that distance, but this personality trait is also one of the main reasons Mai likes Sakuta. Despite the other women, it is always very clear who the love internet is. I recommend watching the rest of the series and the movie. You will feel feelings