
Quick answer — Yuusaku Igarashi worked on Haruka Nogizaka's Secret: Finale (Original Creator), Haruka Nogizaka's Secret (Original Creator), Haruka Nogizaka's Secret: Purezza (Original Creator).
Yuusaku Igarashi worked on Haruka Nogizaka's Secret: Finale (Original Creator), Haruka Nogizaka's Secret (Original Creator), Haruka Nogizaka's Secret: Purezza (Original Creator).