I don't really understand the fuss about the ending of the movie. So lets go back to the movie itself :

Yanase Maki is gay, he has a sick and blind grandmother Midori who wish for him to travel to America. To make his mother happy, he makes ASMR audios for her to relax and make her "see" his various journeys. During his struggles, he meets Ari Naomi. His father Tamotsu is a selfish man who gamble money and ask his own son for money. He will be the reason of his son's unhappiness. Naomi has a girl who is in love with him. But he struggle to have any relationship with her due to his father's dangerous behavior. While Naomi gets closer to Maki while doing ASMR together, he slowly open his heart to him. Maki fall in love with him, but Naomi is still not really completely open to him, for the same reason he can't be with the girl. But Noami decide to leave his father as he has some money on the side to be independent and be with Maki.
Maki, wanting to make his grandmother happy, pretend to have left to America, and with the help of Naomi, give her ASMR to make her believe the story. She died happy, yet Maki think he let her down.

One day, people beat them up because of his father's gambling. Then, when he tried to get his money at the bank, he realised his own father stole everything from him. After facing his father, he has Makino options or he may get killed because of his father, and need money quickly. He decide to steal for a rich woman he knows. But he get caught and go to prison.
Maki came to visit, but Naomi break up with him as he see himself as a failure and want Maki to be happy with someone who can give him the love he deserve.
The conversation is not obvious, but the intension while knowing the story behind his words can't be missed to those who can see more than just the lines said by the actor.

When Naomi left prison, he got closer to the girl he know and they get together as a couple. From my point of view, he just want a quiet, trouble free, life. He already has a record, so working can be a problem, and being with a man (in japan) can be even more difficult. So he has chosen his head instead of his hart (like many people do).
The final scene is the same as the opening, when they see each other in opposite cars. Maki seems relax, yet Naomi will always linger for the one he can never have.

The ending reminded me of More Than Words (2022), when parents have their hands on their children's happiness. Even if japan is not a dangerous country for gays, they are not yet fully accepted. Especially for parents with gay children. But here it's not homophobia, it's the dominion of parenthood over their children's life. It's all about pretending :
Maki fakes his own life to his blind grandmother for her to be happy, hiding behind a picture perfect he made up for her.
Naomi fakes his own love to become normal and escape his father. He also escape his own "prison" made by his dad by listening and playing with Maki.

I get that many people would have loved a love story with happy ending. However, many Japanese BL are close to the French dark movies. Very close to real life, were people are facing the society and the culture of their country while struggling with their own love life. The movie is good. No violent ending and no real homophobia. So it's easier to watch than some other movies. It's a movie to watch at least once.