Mynydd took the lead in the third minute with a stunning free-kick from Tomos Williams, curled right into the top corner.
Tigers equalised immediately via a low finish from Elliot Breaks.
Two goals from Callum Thomas assisted by Lewis Clayton, a side-footed finish from a rebound and beating the offside trap to slot past the keeper in a one-on-one, gave Menai a two goal lead.
Clayton made it 4-1 with a swept finish in the bottom corner.
The lively Clayton had a penalty claim waved away just after half-time, and later found himself one-on-one on 59 minutes and poked home to make it 5-1. Substitute George Roberts beat the keeper at the front post to make it six with his first goal for the club.
Mynydd pulled one back, Tomos Williams again with a wonder strike, this time from an almost impossible angle, looping the ball into the corner of the net.
Aron Lewis-Davies finished the scoring on 89 minutes with a back-post finish from Harry Jones’ low cross.
Osian Hughes and Benn Lundstram both struck hat-tricks as leaders Bethesda hit a magnificent seven against Llannerchymedd.
Both these sides challenged for the Division One title last season and it was Medd who finished on top, although both gained promotion.
On this afternoon, Athletic were much the better, Noa Hughes also on the mark, while Ryan Rowlands and Chris Bennett replied for the visitors.
Luke Baum netted his first hat-trick of the season as Talysarn rattled up nine at home to Pentraeth.
Glyn Hughes-Thomas and Tirion Roberts added two apiece, while Llion Jones and Jac Pearce Jones contributed singles.
Connor O’Neill scored a consolation for Pentraeth, who had Ashley Davies sent off for two yellows before half time.
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