There was a storyline? really? The storyline of Eiken is hard to follow or even be aware of due to it being interfered with the constant fanservice. I find the problem with most ecchi animes is that they focus too much on making sexual jokes and situations, and they forget about the story. Sure, they ecchi moments are nice, but without a story to put them in context, It becomes a "lets see how many panty shots we can fit into 30 minutes" contest. That is the problem with Eiken, it has a decent story, but it is drowned out by the constant fanservice. I think that if the fanservice and ecchi moments where intergrated into the story to make it make sense for it to happen, I would have enjoyed Eiken. But the main downfall with most ecchi animes is that the story almost always becomes secondary to the fanservice and ecchi moments, and the story becomes the slave of these moments, instead of the other way around.
My major complaint about Eiken's art is that proportions are extremely out of wack. I don't mind it when the female character's boobs are a tad too large for them, but Eiken just makes a mockery of it. They are just way too big. If they where real girls they would always be falling over forward and would require a good chiropracter at the age of 15. Plus I also think that it is a bit excessive to give a 6th grade girl boobs that are probably F sized. That is just plain wrong.
Most of the characters I did not have major complaints with. Two characters in particular I did not like where Yuriko and Kirika, who are both complete and total whores. They have no depth what so ever, and all they do is try to arouse poor Densuke. I would not mind them so much if they had more to them than trying to get their boobs as much contact with Densuke as possible. That is another major problem with most ecchi anime, which is that the characters are shallow and the female ones tend to be whores.
Even though Eiken is a two episode OVA series, I would not waste my hour of time watching it, and neither should any of you. Do not watch Eiken. It is terrible and not worth the time it takes to watch it.