"1920 ...?"

Tsukasa Kazami, a young man who lives in 2020, sees himself travel back in time 100 years ago after sitting under a cherry tree.

-- Tokyo, the Imperial Capital. Full of hopes for the future, it's a brilliant romantic city where the flowers of culture are in full bloom.

"Elementary, Tsukasa. The last thing left is always the truth."

A mysterious British woman who runs a detective agency alone in the imperial capital.
Under her lack of money, Tsukasa is involved in numerous incidents ...?

"--Now, let's find out the answer".

Which era will awaken his true potential, Reiwa or Taisho? The curtain of this retro mystery among cherry blossoms lifts!