I feel like the fact “Lending” can be triggered without consent from either the Kyouka/Himari, Yuuki, or whoever grabs his chains is probably going to be important down the road. I can already imagine a scenario where he’s cornered away from everyone, fighting the Thunder Gods when one of them grabs his chain and activates “Lending” upon which once realizing what happened he’ll be forced to fight and likely do a lot of damage to the Demon Corps.
But because he isn’t used to the new form he’ll expend all of his energy before dealing the finishing blow, he’ll then de-transform upon which the reward will be triggered and thus the battle will conclude without bloodshed on account the Thunder God can’t do anything until the reward is given. Maybe that’ll be used to their advantage and Yuuki will be brought somewhere else forcing the Thunder God to follow unwillingly.
Honestly that hypothetical scenario just reminds me of the fight in SMBZ when Mario and Sonic used the Power Star to become Super and fight Mecha Sonic. Only to run out of time right before finishing him off for good.