First of all, I haven't seen the Korean version of this drama, so my review is entirely based on this Japanese version.

If you're into Erased/Boku dake ga Inai Machi (manga, anime, movie or drama), this one is right up your alley. It has the same elements of detective/mystery storyline, a time travel element and the very first case of this drama is similar to the main one in Erased. This story, though, is less focused on one specific character and has various ones whose choices and lives impact the main arc, so it's more fast paced and has more puzzle pieces to gather. I appreciated that a lot.

The cases depicted in the drama are influenced often by real ones, and most of them are very graphic in terms of what they depict, so keep that in mind if you're impressionable. Still, I think they're handled pretty well and showcase the complexity of each one while making them fit on the overall story.

The time travel aspect is done via communication of the two leads, and stories of this kind tend to be tricky because of how they handle paradoxes and whatnot. I think this one uses the trope very well, it connects well throughout and keeps you on the edge of your seat, wondering what will happen next.

As a detective drama, it isn't primarily focused on who is or isn't guilty but on how law and justice don't always go hand in hand. This isn't an ideal portrayal where policemen are always good or where the justice system never fails, it's a story about shades of grey and how what's right isn't always what's fair. Considering the subject matter and the cases portrayed, the focus of the show was impeccable in that sense, and taking into account that there are TONS of detective/police jdramas out there, this perspective is much appreciated.

As it normally happens with jdramas, this version is shorter than its kdrama counterpart. Still, I think the length of this is perfect as it is, it would have dragged too much for my liking in a longer format. There seems to be a Special Episode that apparently is linked to this drama though, I haven't found info on it, so I'm gonna assume it's a side story which doesn't add to the main one in any determining factor, but who knows.

All in all, I highly recommend this drama to those who are fans of the thriller genre, like detective stories that aren't always black and white, enjoy time travel elements and want a story to keep them hooked.