Some comments from MagaPoke.
There are many aspects that feel incomplete, but the smiles on their faces knowing their dream has come true and they're reunited after so many years are truly moving. If she had remained his manager, they would never have reached this future. Therefore, the ending, where even the breakup was a necessary step for their true reunion, is excellent. It's a rare and unexpected happy ending from Professor Airi, who usually prefers bittersweet endings. Furthermore, seeing Shinobu's tears in this scene, something he never shows no matter how painful things are, is incredibly moving.
Another perspective.
It's truly amazing how different people interpret the ending. I don't think the final scene is Shinobu realizing she's been cheated on, but rather the moment their feelings reconnect, and it feels like the light in Sakura's eyes, which had disappeared since she started to suspect, has returned. I hope they include an epilogue in the collected volumes... There must be a missing chapter in the collected volumes. Even without an epilogue, I want to believe they'll hold hands again and get back together.