The mangaka made multiple endings.
The first was Uruka's ending. She was about to leave for America for her trip but Nariyuki managed to confess back to her before she left. When she returned, they resumed their relationship and were talking about marriage.
The next was Rizu's. She was haunted by the ghost girl, Misao (she only appeared in one panel in a chapter so no surprise if people forgot her), and with her and Nariyuki's help, they managed to resolve Sawako's family issues and entered into a relationship. Misao is implied to now haunt Sewako (who moved back home) and Rizu and Nariyuki live together.
Then came Furuhashi's ending. She faked an injury so Nariyuki would take care of her but felt guilty. Nariyuki didn't care and wanted to continue to cherish and protect her. She also finally admitted to Rizu and Uruka she loved him and got their support, so they officially entered into a relationship, finally accepting her feelings.
Then was Asumi's ending. She became an assistant doctor with her mom on an island and Nariyuki was the schoolteacher. He got into a bad accident but Asumi conducted surgery and saved him. It was revealed her dad knew they weren't dating from the beginning and was Nariyuki's dad's doctor before he died. Nariyuki harbored no ill will and Asumi accepted she loved him, making their relationship real.
Now we have Mafuyu's ending. As we can see, Mafuyu has a lot of mental trauma from her past she's having a hard time overcoming but Nariyuki is melting the ice.
She might be the final ending before the manga ends for real or we might have a surprise girl, or harem, ending after. Unlikely, but that's where we are.
Hope this helps!