Ah, another Tengen Toppa Gurren Lagann doujin. Maybe I'll see another GAR doujin like "100% Drill" but when I read this, all I got is just simple fuckfest between Kamina, Simon & Yoko. The premise is simple: 3 of them were trapped underground and then Kamina trying to be funny with Yoko. Simon, on the other hand, played along with his big bro, Kamina. What do you expect? Simon isn't that GAR yet, he's still a boy! Art-wise, this doujin is OK. A lot of bodily fluids here and there and some strange facial expressions - as expected from Tsukino Jyogi. To me, I'll give a 3 out of 5 for the art department - nothing special but nevertheless, it wasn't bad, either. But hey, I had a good time reading this. Body figures are realistically drawn and that's the charm of it. No big-breasted Yoko, too, since I abhorred such dounjinshis.
As for the story, there's nothing much to be remembered. Like I said earlier, this is just a fuckfest between the three titular characters of TTGL. If you wanted something GAR like the anime itself, try "100% Drill". But if just want to fap to it, this doujinshi is enough.By the way, I like the male character ejaculating inside. That's my favorite. Who can resist the urge to cum inside anyway?
So, all in all, "Otona no Drill" is a just-fine doujinshi for your fapping pleasure. Thus, I'll give it 3 out of 5. With realistic art and creampie to boot, I'm sure you will like this too. Just be ready with your Kleenex.