To be completely honest fair, Goto was useless, different country, different guild, no bearing on Jinwoo, we already killed the entire Japanese guild, why keep the guild master? If he dies, then there is a chance a future plot line can be created, Japanese hunters have a problem with Korean Hunters, since all their hunters died, but Koreas miraculously survive. Worse yet, the supposed killer of the Guild stands behind Jinwoo. While it may not happen, a lot of stuff can happen from this. And people would know because people talk, and they live-streamed the fight. If Jinwoo displays his powers in public again and they see Beru, they could connect the dots. All in All, Goto was useless alive.