IF YOU HAPPEN TO SEE THIS BEFORE THE MOVIE WATCH THIS BEFORE THE MOVIE ❗❗❗ The order you watch both this OVA and Movie will change your perspective on the 2 Main Characters. I am so glad that I listend to a random youtuber's advice to watch the OVA before the movie and it might've been the wrong intentions of the author but you will understand everything about the movie more clearly without massive spoilers and because the movie will be a great end to this watch order because of the good ending while if you watch this OVA last, you will only see his depressing struggles withno reward.

Depending on which order you watch first, you will side to either the younger or the older MC, since this OVA focuses on the older MC you will understand his actions more and how much he has gone through, but if you watch the movie first, you will side with the younger MC and only see the older MC as just a villian which is absolutely misplaced anger.

FINAL CONVINCING :
Its only 3 episodes 20 minutes each and even available on Youtube.

I hope im not too late and you already watched the movie, but if you ever decided to rewatch the movie, follow this amazing order.