Fate/Incursio

After surviving the revolution that tore his homeland apart, Tatsumi wanders the earth aimlessly, Alone and burdened by his past, his journey takes an unexpected turn when he's summoned to a new battlefield-this time as the Berserker of Red in a grand Holy Grail War.

The prize? A wish-granting chalice that could rewrite the past and undo the tragedies that took place all those years ago, What a chance to rewrite his fate, Tatsumi faces the ultimate choice: to continue fighting for the future or risk everything for the chance to redo it all.

But why does he feel as if this is all for the amusement of a vampire troll?