Erased

Both drama tell you about the time travel concept with romance and thriller as the genre.
Both drama will make you confuse at the beginning with the gloomy situation of the main lead. Then slowly but sure..the facts that they want to change are revealed. Both drama shows how the main lead try to protect their lover through the time travel. Also, the most similar part is about psychopat act that later on can explained how it will give big impact to the critical situation in the past.
And no matter how many times the main leads try to go back to the past, the future result is getting worse than ever.

Watch it if you love dramas about time travel and particularly stopping crimes from happening. Both are amazing and will leave you craving for more. Smart male leads.

Homicidal events of the past collide with the present.
The actions of the ML in the current future could alter the past and, thus, alter his own destiny.

Both have a murder case involving their parents
Both series are about trying to solve their mothers murder cas.
Both are a thriller, crime and mystery genre

Differences:
Erased is adapted from a manga
Erased involves time travelling, Ugly takes you back by looking back in the past by memories.
Erased is a micro JDrama
The Ugly is a Korean movie.

Both try to solve cases through time travel

Both: thriller, crime, fantasy, mystery

The difference:
In Erased ML becomes a child again and sees this opportunity as a second change to prevent this from happening.

In Tunnel ML stays the same and teams up with a new investigation partner.

Both are adaptations from a manga that contained elements of time-travel. And amazingly enough, both also involved an incident set in Hokkaido while the protagonist was currently based in Tokyo. Also, both involved the protagonist being from a future with bad outcome ending up returning to the past to try to prevent incidents happening in order to change the past and future.

Both involve the main character time traveling back into the past to save a friend and almost the same ending too.

Both make use of similar tropes, and due to the nature of the endings, I think one inspired the other.

Didn't watch Nine but I feel like both will be similar in terms of time travel and stopping crimes from happening. "Boku Dake ga Inai Machi" was amazing and it is derived from a manga.

Although there are differences with regards to what triggers the time travel in both the dramas the male leads tries to prevent a tragedy from happening and how his efforts leads to a butterfly effect and changes events . In Meet me @1006 romance is important while in ERASED priority is given to prevent the tragedy .

Both involved male lead travel back in time to prevent the dead of their love one
Can they change the future when there were back to the past.
Fun, intense, mystery time travel film to watch

Both films involved male lead travel to the past to prevent something to happen, to fix things, for the love one. Can they accomplished their mission? Can they fix and change the future?

Both are good Japanese film to watch. They both involve male lead travel to the past to fix something. Both has some romance. Fun watch. Love both male leads. Worth watching.

Protagonists both know what will occur in the future. I experienced the same mystery thrill!!! I loved the adrenaline I derived from both.

Both involved male lead attempted to correct the past.
Will he be able to change the future?
Does he has the power or ability to amend the future event?