Tatsuha Uesugi, younger brother of Eiri Yuki, shares identical facial features and voice with his sibling but is distinguished by stark black hair and eyes. Documentation discrepancies list his age variably as 16 or 21, though all sources acknowledge his role as a Buddhist monk or priest-in-training at his father’s temple. Contrary to monastic expectations, he directs obsessive focus toward musician Ryūichi Sakuma, compulsively watching archival footage of Nittle Grasper performances and exhibiting fanatical, occasionally transgressive behavior. He routinely neglects temple obligations to pursue fandom activities, even donning a blonde wig to impersonate Eiri and mimic his brother’s appearance. This conduct underscores his recurring pattern of conflating personal identity with fixations on others.