Suigin Becomes the Last Tomb Guardian!. Riku Yuuki explains the game of Grave Buster to Suigin. In the game of tomb raiding and tomb guarding that has gone on for years, Riku Yuuki ended up being the one and final guardian to guard the Goddess’s tomb. Suigin finds out that guarding the Goddess’s tomb is connected to protecting Riku Rei, as well, and tells Yuuki as he is fading away that he will become the last guardian.