Dai is a minor character from Ninja Gaiden.
Dai's corpse can be found at the top of the Stairway to the Imperial Palace, after Ryu was cursed by Doku. His diary reveals that he had obtained the Key of the Decayed Soul that allows entry into The Core and was on his way to meet with Gen. Though he was gravely wounded he was able to make it to palace doorway. But was unable to get past the locked doors.
When Ryu unlocks the doors from the inside, he finds Dai barely holding onto his life. Though it dishonored him, Dai gives Ryu the key to The Core, urging him to defeat the Vigoor Emperor. He then dies, asking for forgiveness from his master.