Kasimasi - Girl Meets Girl OVA
If you enjoyed the original series you'll probably like this, especially if your a Tomari-chan fan. If you've never seen the series, a boy "Hazumu" confesses to a girl "Yasuna" who rejects him. Hazumu dejected climbs a mountain that evening, an alien ship accidentally turns Hazumu into a girl. Now Yasuna kinda likes Hazumu, who was admired by Tomari since he was a child.
You can download the bit torrent file for this episode from GNU Fansubs here. I posted a Youtube video of the opening after the screen caps.