You probably shouldn't be. Using Flare against the Heroine with only partial protection from Fated Love can lead to the costs of using it very rapidly ballooning upwards to unacceptable levels.
Shitty posts like this is exactly why I'm so confident of managing to push Azure Flare.
No matter how much you people like to push "b-but muh cost" bogyman, I can easily debunk it with
If you took Do It For Her + Bonus (Azure Flare), you could get all three components needed to kill the Heroine before the year is up, in theory! Fated Love resistance from the Oath, esoteric offensive from Azure Flare, and your already have the needed power level.
Note the distinct lack of "although this won't work because muh cost"? This and few other posts have Rihaku mentioning that Azure Flare is actually the way to go if we want to kill Heroine, despite what "it will totally kill us" crowd wants to believe.
Meanwhile, Truth Incarnation will remain least efficient option because a) We can't use Magnum Opus part b) Mind immunity is redundant with L-D+DIFH c) Stage boost is of no relevance against Heroine and d) It can't boost Azure Flare until we get it.
I actually don't understand why you guys like pretending that Flare is unusable. We already see base Essence cost and it's literally negligible. As in, Cultivation cost from True Spells is actually not factored anywhere.