A manga/comic by the renowned pokemon fanartist Soara, entailing a young Satoshi and his troubles with a certain pokemon.
Based on the mysterious addition of Route 21's grass patch south of Masara Town.

Kenn's Comment: For those not familiar with Pokemon, Masara Town is the Japanese (original) name for Palette Town, the hometown of the player character. Route 21 is only accessible after getting Surf, and, if starting from Cinnabar Island, which is Gym #7 I believe, it ends with a single grassy patch before entering the town. Compared to the wild Pokemon in Route 1, the other exit of the town, the ones found in Route 21 are considerably stronger.

Anywho, soara's undoubtedly one of the greatest Pokemon fan artists I know of. I usually drop in for his/her 4 koma, a hilarious mix of game mechanics and ridiculous antics. But this one was quite different. Not a comedy, but rather a horror story, based on the strong Pokemon found in the route. The title picture should be a dead give away of which Pokemon it's going to be focusing on: everyone's favourite tentacle rape Tangela. Prepare to be creeped out and never look at a Tangela the same way again (though honestly, I never did like Tangela).

Also, no actual Pokemon battle. It's less of a 'Pokemon'  and more of a horror story set in the world.

Edit: And it reads left to right. Almost forgot to mention that. Caught me off guard the first time I read it.

For those who follow the English dub, Satoshi = Ash Ketchum.

Read it over at Pixiv, or Danbooru