Just wanted to point out the fact that Takumi’s hand is shaking when he and Sento fuse together. I want to say that this very scene has a symbolic meaning. Takumi is scared about what will happen in the future if he’s not around, he thinks that things will end up getting worse, I mean lets be honest, things did get worse while he was Sento, but his trust in his other half, his other half obviously being Sento, as well as the memories that he ended up regaining as his time as Sento, gave him the push to give up the reigns, and that he was willing to let Sento live on in his part. I guess you could consider Sento as Takumi’s living legacy, which is HONESTLY what Sento is. Takumi Katsuragi’s living legacy; a man that is, and yet isn’t Takumi.
Going to be honest though, I really hope I’m not reading too much into it, but I probably am.