Strike the Blood, Vol. 6 (light novel): Return of the Alchemist by Gakuto Mikumo
When all the students depart for a school field trip to the mainland, Koujou is delighted to hear that he'll finally get a chance to be free of observation for at least a little while, while Yukina has mixed feelings about the whole situation. But events move quickly when an alchemist by the name Kou Amatsuka appears, with the goal of reviving the holy grail of alchemy--the liquid metal lifeform known as 'Wiseman's Blood.' As the crisis deepens, even Asagi becomes involved as this relic of alchemy grows more and more uncontrollable. What can the world's strongest vampire do?!