Tomochika Izumi

It's the 30th century and time travel is illegal. To help monitor and police time crimes, the Time Protection Department is founded. But when Don Dolnero and his nefarious gang manage to trick four new TPD cadets into allowing them travel to the 20th century, the four cadets are forced to pursue them for the sake of history. There, in a time foreign to them, the cadets enlist Tatsuya Asami, a young martial artist, to aid their mission. Together, these five youngsters become the Timerangers. And though they try to live as ordinary 20th-century citizens, the Timerangers dedicate their lives to stopping Dolnero and others that may follow in his footsteps, attempting to forever alter the proper timeline!

Asai Takuma is a fourth year college student who is having a hard time finding a job and is desperate for the sake of his future with girlfriend, Shintani Risa. One day, he was asked out by his childhood friends Eiichi and Mamiko to dig out a time capsule that was buried 10 years ago. The time capsule contains a letter from Takuma himself in the past. However, Takuma also receives a letter from himself 10 years later with a "shocking future". He decides to collaborate with the future him to change his life.

The protagonist, who is looking for an apartment, accidentally opens a door to another world. There, she finds herself trapped in a huge, desolate building. It is a hellish place ruled by a certain monster, where neither going out nor dying is allowed!