There is a BE expansion in oppai heart 2, what I know about this hentai is that these girls have some virus that makes their breasts bigger and hornier. To make a vaccine the guy has to get these chicks pregnant make an antidote.
BE is at 10:50. If the download doesn't work I can link you the torrent since I don't really know the rules about linking to them or re upload it myself to another site.
Credit to taekmkm for the upload
http://turbobit.net/s0ld35evqr0f.html