Major spoilers for future reference (from Calamitous Intent):
The ending of the game is considerably different from that of the anime. The latter had the dramatic scenes, where Renji saw Chihiro lose her memories, where Chihiro struggled to preserve her love, and of course the amazing climax. But the ending was a tad... unrealistic, I suppose. The ending in the game was less dramatic but so much more real. Renji chooses to start his relationship with Chihiro afresh, even though he had the pages of her diary in which she wrote that she loves him, he chose not to give those pages to the Chihiro when he meets her again. There’s something endlessly sad about this, but it was beautiful and hopeful.