No one can truly understand Dazai, and no one can fully enter his world.
This time travel happened because everyone wanted Dazai to be happy.
In the end, Dazai felt it and tried to respond (but still wanted to embrace death)
Because Dazai is a coward and has no ability to love.
At the end, Dazai couldn't help but smile when he recalled the magical experience before. To this day, he still can't tell whether it was a dream he had or whether he really went there, but it affected him after all.
Finally gain happiness and return to the original world
This time travel is more like having a long dream
Purpose: Give Dazai a good ending and let him let go of his burden