I just read a funny little (it's too short! D:) story on Fanficton.net... Frisky Business. I laughed so hard... Mitsui's so mean! But I so love him in this. Rukawa's great too. I really recommend this for anyone who's a fan of SD, humour, and a little yaoi (not actually yaoi, but they almost get to it... it's very sexy). It's not really one of those "this is so real... it could actually happen"-fics, as someone pointed out, but it's still great. And did I say that Mitsui's great?
A few months ago, when I was desperately searching for some SD goodies (it's such a shame that there's nothing new coming up... the newest fics are two years old and all communities everywhere have died... I've only found raw djs, well, maybe there are translated Sakuragi x Rukawa ones, but as much as I love Sakuragi, I really hate that pairing >.>), I came across a Fanfiction.net community named Blue Eyed Hotties. Guess which pairing that com is dedicated to! ;) Well, it's kinda dead since there haven't been any new fics for a few years, but there are 89 fics and that's enough for a while. Though, at least I can't get enough of this pairing. I learned to like Rukawa because of Mitsui... However, since it's pretty hard to find MitRu fics, I thought I'd link that community in case there are some MitRu fans out there who haven't found it yet. It took a while for me to find it, too.
The short oneshot that I recommended was also found from that community. Go there and look for some other ones. And if you come across more MitRu goodness, please inform me via PM or by commenting. I'm kinda slow at finding things by myself, so it might be that I haven't found what you have. :)