The main character is Rintaro, an engineering student with an interest in weird gadgetry. He styles himself as a mad scientist, changed his name and constructs 'future gadgets' in his lab in Akihabara -- aided by an otaku hacker and a childhood friend who works in a maid cafe. And then everything changes because one of the future gadgets, the cellphone microwave, turns out to be a time machine. The lab acquires quite a few new members in a short time, most notably a brilliant young engineer who helps theorise the new time machine.
[Of course, things go pear-shaped after that]
You can play around with it for a bit, but when people start sending mail messages to the past, the past changes -- and people's memories with it. Except for our main mad scientist, who retains his memories of how things were before. That in itself is bewildering enough, but then CERN comes to shut down his operation: they are the only ones with a time-machine, and they want to keep it that way! Add in a mysterious time traveler who claims to know all about CERN and the future, the quest to find an old PC from 1974 and the inevitable death of one of the lab members, and you get a frantic cat-and-mouse game through time -- all in the course of a few weeks.
Even though Rintaro has a bad habit of making an idiot of himself and others, he turns out to be pretty dependable and resourceful when it's needed. Because he is the only one who can travel back in time and retain his memories, he's pretty lonely -- having to explain it all again and again and again to the same people. But in the end, he pulls through and even manages to prevent WW3 from happening!
The series isn't action-packed. There are whole episodes that are not much else than the characters walking around Akihabara and theorising about the nature of the time machine they built, or hunting down a certain person or part. But every episode, there's something that shows that there is more than is known at that moment, and that the truth is actually grander than anybody knows.
Because of the small area that is covered, it gave off the same feel as Durarara -- you have all these characters interacting as a group and separately, encountering each other as they go about their business.
It's a brainy series, which makes you think about what is happening and what will happen next. Sure, I'm interested in stories about time travel, but I think that's not the only appeal. The creative story-telling ranks very high.
I think it's a must-see, so I'll give it a 9.