ok so first, it's all right i have commited the same mistake in regards to the annoying button. secondly, sword planned the whole thing with the FBI, which was Walter page 198 and you see that by the message sword sent sen on page 187
http://www.mangago.me/read-manga/under_grand_hotel/an/under-grand-hotel-chapter-Volume%203.html/187/
sword also warned sen about the shooting that would come after in page 189. Sen followed the orders of sword that was in the message and reunited with him so that the plan could get in action. the plan being faking death. this plan was granted by the FBI in exchange for sword (the top dog in UGH) coperation in exposing thw Warden and his drug dealing. by the way the Warden used books to smuggle the drugs in the prison. page 199. also sen said they "checked out" of the Hotel in page 200. Hope this helps.
Ok so technically they aren't dead. Sword said that because ugh( the underground hotel, which is prison) thinks they are dead because that was the plan. To make everyone think they are dead which worked also right now the are in an island away from the location of ugh. So that's the basics. Sorry this is my first time explaining so it's vague. Hope you understand. Also this is a really good yaoi plot.(≧∀≦)