If you play the game, there's a side quest to help NPC in belobog. Few of them are like remnant of their obsession lingering because stellaron thingy that we need to help/ clear so they can go to afterlife(?) aka disappear like on this comic. I believe the soldier is one of the Gepard's childhood friend and died when there's monster breakout. The soldier might have a little crush for Gepard and couldnt let go, so when he see the interaction between Gepard and Sampo, he feels repulsed but on the story goes on he knew sampo is not that bad. So back when the soldier meet the trailblazer (MC who promise the Soldier to slap Sampo with a bat) he kinda let go and that's it. So yeah, the soldier is like wandering spirit/ghost (=・ω・=)
OoOh I see thank you for explaining I haven't played the game so this really helps!(≧∀≦)
I- well don't know how too feel about this so confuse and horny at the same time btw like who was that other guy? ╮(￣▽￣)╭