is Lala's personal bodyguard and the best swordsman on Deviluke. Initially, Zastin disapproves of Rito, deeming him weak and subsequently seeks to test his strength. However, once Rito exclaims his opinion of marriage in self-defense, Zastin is swayed by his words, though not in the way Rito intends, and summarily approves of him, believing he truly understands Lala's feelings. He is currently working as the assistant chief to Saibai; the funds he gets for his duties are handed to Lala for her use. Zastin has shown a keen interest in becoming a mangaka, professionally. He has two assistants that work under him, simply known as Maul and Smutts. Zastin's tail is thin and very scorpion-like in appearance.
Despite his skill with the sword, Zastin has a horrible sense of direction, resulting in him getting lost (one of the running gags in To Love-Ru). He also seems to have extremely bad luck, where he keeps getting run over by trains and cars.