You guys are pretty dim. The very first time Takopii uses the camera to travel back in time, he says it's because he wants to understand Shizuka so he can understand what could lead someone to take their own life.
Instead, he adopts a hero complex and relies on a reset switch to try to solve her problems while knowing nothing about her or her situation.
It's only once he finally becames able to understand Marina and Shizuka that he realized that their problems could not be solved by an outsider ("there's so much I can't do for you") and that what they really needed was someone by their side who could understand their pain. That's why the happy end is the two of them finding happiness in friendship in one another.
This really wasn't subtle and you're retarded if you missed it.