If Romance of the Three Kingdoms XIII generated the same gross revenue on the Epic Games Store, KOEI TECMO GAMES CO., LTD. would keep approximately $10,787,913 - that's $2,195,942 more than on Steam.
At this revenue level, Epic's concrete platform fee would be $1,334,715. Epic charges 0% on the first $1 million in annual per-app revenue and then 12% on the remaining amount. On GOG (30% cut), the developer would earn approximately $8,485,839.
Note: This is a hypothetical comparison. Actual sales volumes differ significantly between platforms, and Steam's larger user base typically drives substantially higher sales.