Under Grand Hotel (UGH) is the inmate's name for a prison in the US.

Sen is a Japanese guy who has been imprisoned after killing his lover's husband. As expected in prison, there is always the fear of getting raped by multiple inmates. Unless he can secure the protection of a powerful inmate first, his ass belongs to everyone – literally! Aptly named Under Ground Hotel, this maximum security prison in situated entirely underground; but those who had come to rule it and love it, prefer to call it UNDER GRAND HOTEL.

This is without a doubt, the smuttiest manga you will ever read!

Sword Fish – the current prison boss is a dangerous man. Other inmates fear him, and take utmost care to be on his good side. What Sen doesn’t need to do is pick a fight with him the first day he arrives at the prison; yet, that is exactly what he does! What will happen to Sen now? Did the situation just get worse for him, or will he manage to rise out of it alive? Will there be somebody – just anybody, helping him in this volatile place or is he cursed to rot in here all by himself? And what of Swordfish – the prison boss with the deep cerulean blue eyes? What are his intentions for Sen? Is Sen doomed to rot in here for the rest of his life, or will he be one of those lucky ones who get to call this place UNDER GRAND HOTEL?

Warning: very graphic and explicit*