Steins;Gate 0

A few months have passed since the members of the Future Gadgets Lab inadvertently unlocked the power of time travel using a phone and an old microwave, but for Rintaro Okabe it may as well have been an eternity. While his friends' memories remain mostly hazy, Okabe can still clearly recall crossing over hundreds of world lines, watching as his friends suffered and died innumerable times for meddling with the fabric of the universe. Though he ended up saving the life of his best friend Mayuri, Okabe is still suffering from the trauma of being unable to prevent the murder of the brilliant young scientist Kurisu Makise. He has focused on forgetting the past and moving on with his life, but he is constantly reminded by future freedom fighter Suzuha that their current world-line is set to be torn apart by a devastating Third World War, and all of the Future Gadget Lab members will be caught up in the struggle. Okabe must decide whether he will once again fight the future one final time.

Synopsis from Anime News Network