Ano Ko No Kawari Ni Suki Na — Dake Work __hot__

The "solid" emotional weight of the story comes from the internal struggle of the lead characters: The Surrogate:

The work’s ending varies by adaptation, but the strongest versions leave the protagonist realizing too late that the “instead of” girl was never the replacement — he was the one who failed to see the real person in front of him. Whether they part ways or painfully rebuild, the final message is clear: