I Saved Too Many Girls and Caused the Apocalypse

Rekka Namidare was a normal boy until his sixteenth birthday. Then a girl suddenly appears from his future, warning him that he'll somehow start an interstellar war! It turns out Rekka hails from a special bloodline that's destined to get caught up in all kinds of trouble. Whenever a story's heroine is in dire need, Rekka will be given one last chance to save her. And in the future, Rekka will have saved so many girls that their jealous love for him will cause the apocalypse!

[From J-Novel Club]