Sekaiichi Hatsukoi for me :). it was my very first yaoi manga and it continues to be my favourite. Next up at a close second is Hidoku Shinaide. There's also Elektel Delusion, Dakaretai Otoko Ichii ni Odosarete Imasu and Kuchizuke wa Uso no Aji. I've recently started reading yaoi and so far i'm loving it! reply
