Gamewith's recommended EMP build for Mikazuki Munechika.
Priorities
Prioritise Light ATK first, followed by DA and CA DMG to increase his firepower. His Extended Mastery Support skill doesn't give him 100% resistance at level 3, but with few other masteries and due to him being a character with clear (if faced against a skill sealing debuff), it is worth considering. You can take Healing EMP as much as needed, and the rest of choice is relatively free due to him doesn't have many good masteries.