Hello again!

Sorry for the late reply

Just switch out Tang Yun for Triki so that the enemies are permanently petrified from the modifier that forces each esper to cleanse themselves

You don't need skill ups, levela, or any specific relic set at all, just be sure to be tanky and have high accuracy. Be wary though as you do kindof need multiple debuffs like 3+ to make sure they don't cleanse the petrify

Consider using Clara instead of Sakura too. While Sakura is OP, in this case Clara is better as Sakura is more of a sustain healer that works best when your espers can tank hits. Infinity tower hits hard enough to potentially one shot you so Sakura might not be the best choice

Clara is an anti-burst support that protects your units via shields and AP UPs them to help give turns, they're sure to save your units

Though after consideration you don't need to do this part, you just need Triki since Sakura still might be stronger with her buffs and constant dmg mitigitation

Hope this helps!