Tatsuhiko Saku  

, 佐久 辰彦

Saku Tatsuhiko is a minor character in Toaru Majutsu no Index who leads BLOCK, a faction on the Dark Side of Academy City. On October 9th, he attempted to lead his group, consisting of 5,000 mercenaries from outside the city, in an attack against Aleister Crowley as part of their plan. However, GROUP was able to thwart Saku's plans.