Spider-Man: No Way Home sets up a universe where MJ isn't an option for Peter Parker, but Black Cat's debut in Spider-Man 4 could solve this problem. Through the first three Spider-Man movies in the MCU franchise, Tom Holland's Peter has always had a love interest, be it Liz or MJ, so it stands to reason he will have one again in the next Spider-Man solo outing. In Spider-Man: Homecoming, Peter has had a crush on the character Liz for so long that his best friend Ned pushes him to talk to her. The arc of the story in Homecoming features Peter slowly gaining the courage to ask her out, only to disappoint her at every turn, which is par for the course in a Spider-Man story. Though they do go out eventually, Liz has to move away due to her father's actions, so her character journey is completed by leaving Peter Parker's life.
At the very beginning of Spider-Man: Far From Home, Peter sets his sights on MJ. He doesn't skip a beat when making a plan to sit next to her on the plane ride for their school trip. The first dialogue that Peter has in the movie is outlining this plan, which involves sharing earbuds and presenting MJ with a black dahlia necklace, which is her favorite flower. He's taken the time not only to learn more about MJ since the events of Spider-Man: Homecoming but seems to have completely forgotten about Liz. From the point that MJ discovers Peter's secret identity, she is his main love interest.
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In No Way Home, MJ and Peter are all-the-way dating, up until Peter's impossible decision to save the world. At the end of the movie, he has Doctor Strange cast the spell that makes everyone forget he is Peter Parker, even those closest to him.
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