Y u must watch it?
1)Unconventional badass ML character and for his fabulous acting.
2)Humor-i laughed out loud in many places
3)Interesting twists and turns on each episodes
4)Fast paced time travel drama-No confusion in understanding the concept.
5)I enjoyed it. I hope u will enjoy it too.

Kudos to the whole team(Not only main leads .everyone acted well).Particularly writers did their job well.

Need to mention about Main leads acting .
Yamazaki Kento-What a excellent actor he is!!!Whole dramas focus was only on his character .but wowww.He did a fabulous job!Not sure How boldly he accepted and acted in this character ?! Its one of the badass/selfish/ruthless negative hero character i have ever seen.
I havnt liked FL wen i first saw her on screen. But that was my very wrong judgement. She aced that weirdly cute character so well in screen.

I will suggest to watch it till the 2nd episode patiently to understand the story first, I am sure u wont stop until the last episode.