Well, that was a speedrun of a story, it was obviously made to be released at certain number of chapters but mangaka decided to finish the story till the end, but cut unfortunately a lot of context.
Story of a wish fulfillment, both Riku and Ayana had traumatic past, coped on their own way with experience that changed their lives.
Ayana made a delusional world, where her parents gone on business trip and changed her appearance in school, so nobody would connect her elementary school self with highschool personality, but still remained the same elsewhere.
Riku distanced himself from everyone except his childhood friend Haruno, who he had support through hard times after loosing parents and blaming himself for sister death that he had a fight before accident, which made her not listen to him to wait for him joining his parents in the car accident.
Ayana delusion was her not remembering parents suicide, for him was guilt of making his sister mad at him.
Haruno was a very good friend, it's a shame she didn't understand how Riku fell in love with her, until he found his true love after she thoughtlessly rejected him, after all she didn't had any other relationships before and that was something completely new to her. It's sad in the end, it was a third time her heart was broken and there wasn't any other classmate or person who could heal her heart.
Kana being a closest friend to Ayana, seeing how caring Riku is but that is taking a toll on him, fell in love with him despite her friendship with Ayana, but that was when Ayana lost her memories of them together. Still it was just her trying to not make Ayana remember her traumatic past and sacrificing herself for them be at pace, kinda odd way but after things going back to normal, asked Ayana for forgiveness so they can still be friends. Too bad there wasn't anyone else to keep her company...
Happy that eventually Riku and Ayana came together despite him loosing memory, they were really meant for each other despite shared traumatic past. Even getting married, which was a big FU to Riku grandmother who blamed him for all the people dying around him.
In conclusion, story about two broken mentally teenagers, making up their shared traumatic past through forgiveness and support in hard times, but also sacrifice not only physical but also love love in favour of at least one being happy.
Overall, nice story, sadly it's very rushed, should be at least twice as long but that's how ruthless Japanese manga and anime market is.
7/10