I read this manga some time ago, its about a man coming back to his lover Aoi, a cute boy but when he comes back he finds a huge man instead. The man says that he is Aoi's brother but afterwards the lover sees him trying on Aoi's clothes ( lingerie). The "brother" admits to being Aoi and having repetitive growth spurts during their separation.

Thank you for your help... oph 🙂 🙂

[img]http://th07.deviantart.net/fs71/200H/f/2012/323/5/b/yaoi_smarts_2_by_riposa_inpace-d5lje4k.jpg[/img]

Bousou Kareshi chapter 5? But his name is Rihito.