- Hey, Im GIVING AWAY my GRAVITATION HENTAI DOUJINSHI set! The only thing you have to do is go to the above link and checkout using one of the trials, and i will mail it to you 100% FREE! Yea, just signup for a trial and then cancel it the next day for all I care!!! and I will still mail you your Gravitation doujinshi! The set includes Gravitation Volumes 1-11, Yaoi, and Extras. Just click the above link for more info. Thanks!