The guy below me doesn't quite understand the appeal of this game, so I came here to even out the scales.
The Mercenary's Adventure is a game by a very hardworking and extremely talented gamedeveloper Takamakuran. His previous games, as well as this one, are known for quick, dynamic, mostly non-committed lewd action(which, once you get into the game's rhythm, will actually start to appeal to you, due to how eroticism is presented in this game) and engaging story that, at first, doesn't seem much. But then, once you start digging deeper, you start finding... some rather curious details. If I were to compare his games to mainstream media that is known to most of the folk in the West, it would be something akin to Undertale in how the story is usually layered and hidden underlying themes.
This game has all of that which I described, however this particular title is different from the previous ones in a sense that the story's direction took upon a more common jRPG trope of a hero who eventually starts fighting against the greater threat in the usual jRPG sense. While it might seem weaker than previous titles, this one still has a few twists and turns that you can expect from this developer, and they spice up the experience quite a bit.
The characters are all pretty charming, and even if some of them have little in terms of dialogue - their design compensates for that. Artwork style in Takamakuran games is something called "oekaki" or a "doodle", child drawing-like pictures, and while some might be turned off by that by looking at the previews, many might become entranced by it once they actually get into the game. Despite the rough linework and sketchy(no pun intended) look, the art presents pretty high anatomical accuracy, which is especially noticeable during lewd scenes. Not only that, but the scenes themselves are very dynamic due to high amount of layering stills with text SFX and masked lighting, which further adds to eroticism.
All the enemy sprites are also drawn by the developer, which shows how far he was willing to go to give the game its own unique look.
From my muddled memory, it's hard to say anything about the music, but I do remember not getting turned off by it, so it's at least average.
And there is battlefuck(cat fights), it's just very selective. Most of the fucking usually happens after the fight, if the enemy is fuckable. In fact, you can pretty much fuck every female character in the game, enemy or not. The amount of sex scenes is simply insane.
All in all, this game is a labor of love, and it shows. Make sure to support developer if you liked it, we definitely need more games like these.