Because of Dimension Duel rules you are free to summon high-leveled monsters without tribute. This lets you easily summon the Jin monsters.
The Jin monsters share the effect of reducing any attacking monster's ATK to 0. This deters Aigami from making any attacks.
Since a Jin can only use its effect once, Aigami will occasionally attack into your Jin if succeeding attacks will result in your loss. Also Evilswarm O Lantern might be a problem. All you can do to prevent this is to summon multiple Jin.
Heal every turn with Golden Ladybug and Solemn Wishes.
Thin your deck with draw effects.
Before your final turn you should have 3 monsters on the field.
On your final turn, summon The Winged Dragon of Ra and give him your accumulated LP.
Take note that Lvl 40 Aigami has Field spell Mystic Plasma Zone, which will make Vassal's ATK become 1200 and rendering Secret Pass sometimes obsolete. I always bring a copy of Stop Defense just to make sure.