I'll try to explain without ruining it, set in Japan, the main character is an essentric student who has the persona of a mad scientist who creates gadgets of mixed purpose. When attending a conference about time travel, he runs into a girl who moments later is stabbed to death. He sends a message on his phone to find out the message he sent was chopped up and sent weeks ago and that the girl he saw dead is alive again.

The first half is more focused in the experimental side since they find out the time is linked to one of their devices while the second half is dealing with the butterfly effect of messing with time.