I have played RJ01405813. It was pretty good.
The gameplay was decent. It's a pretty simple game overall and mostly consists of shooting enemies as they approach and then using your dodge with generous i-frames to ignore their attacks but there's also elements like ammo management and picking the optimal gun for the enemies you're seeing so it's not completely mindless. Don't get me wrong though, it's not really at the level that it would be worth playing without the h. It's a bit too linear with just 1 or 2 branches per stage for dead ends with new guns behind them. The game is nice enough to give you a free copy of each gun at the start of the next stage too so you don't have to worry about missing them permanently. You occasionally have to navigate some instant death industrial accident machines but they aren't combined with enemies or anything so this is pretty trivial. The bosses are more of the same shoot them until they die and don't get hit, but since unlike normal enemies they have larger attack ranges and a lot of hp you do have to care about what they're doing a bit more. I thought I set the difficulty to hard before starting the game but when I checked later it seems to defaulted back to normal so that's what I played on the whole way through.
The h is mostly gruesome guro. I don't particularly care for guro so I won't comment on it. Maybe 1/4 or 1/5 of the scenes contain some kind of futa sex though they sometimes contain some amount of guro as well. The bosses get full CGs for the GoR while everything else gets the same autopsy CG showing her corpse edited to reflect the damage the enemy's kill animation caused. The art and animation are great, though I would certainly hope it is considering how much the dev is charging for the game. There's also 2 bonus animated futa scenes that are only available in the gallery.
Overall I give the game a 4/5. Not really my fetish but I do like the art and find the death animations neat.