Diavolo's Crossover Character Development Plan

Have you ever had the worst day of your life?

Mr. D, who exchanged vows with the woman he loved in a church only to die a second later, says nothing could be worse than that.

But reality tells him there is something worse:

He transmigrated into Diavolo.

Reader's guide:

1. A serious story. The author's most negative work. OOC and personal interpretations are unavoidable. If that's not for you, click away.

2. The update speed depends on the comment count. As long as you join me in tormenting Mi4da, we're friends.

3. The password is Qi Liu Liu Jiu Ling Liu Si Liu Er. You know what I mean, right? (Hinting desperately.)

Theme: How a split personality comes to be