I will be talking about the 2 episodes OVA not the 6 episodes version just to clarify this. Will watch the later one soon.
I''s is actually a manga series in Japan which is basically a teen drama romance. It might be one of the 1st manga I read when I was in high school and love it ever since. This 2 episodes OVA isn't following the story in the manga at all. Think of it as a side story but it doesn't follow anything from the manga and you're not missing much at all if you don't watch it.
All the major characters from the manga is in the show but only 3 of them are development a bit more than the rest. They is a new character only in this anime but he won't be there long. You follow the main character Seto who went to a resort where his friend/secret lover, Iori, who is having a photo shoot at the same resort. At the same time, Seto childhood friend, Itsuki, is going to the same place where both her, Seto, and a mystery boy make a secret pack 10 years ago to meet up again. That's basically a rough idea of the story. What make this story bad is it didn't go anywhere really and how it end make it feel like they is no point to make the show at all.
Yes, the new character (mystery boy) feel tack in as no personality was shown during the show. This is fine as he was kill near the end of the 1st episode (which make you wonder why make a new character at all). Don't worry he come back in the 2nd episode as a ghost and still nothing much to say about him to the point you can change him with a rock or a tree and you're not missing much after that. He just there to push the story forward really.
As for animation, it's fine but feel like the people who make this OVA have a very limited budget and you see it in the animation on the characters. Just an observation from what I see.
Overall, I won't recommend this show to anyone as they isn't really a point to watch this. I would consider to look into the I''s Pure OVA as that is based on the manga and if you're fan of the manga (or want to have an idea) go for that OVA.