Possible Clues:

• L'Arc-en-Ciel frontman
• First president
• Jekyll's alter-ego
• Novella by Robert Louis Stevenson, 'Strange Case of Dr Jekyll and Mr --'
• Part-time doctor in philosophy department
• Jekyll's other personality
• Park doctor turned into during work
• Villainous alter-ego
• R.L.S villain.
• Literary London villain