Renial getting frustrated because he is unable to catch Viffrin because he might be a threat to Giselle not knowing in the future chapters he actually 
Spoiler!
Succeeded to poison Giselle which made her lose control and was brainwashed into stabbing Renial so that Viffrin can take Renial's powers. But when Giselle realized that she hurt Renial, she started to cry and all the neutral magic surrounding her was absorbed by Renial which healed his mana vessel and his injuries while Giselle lost her memories as side effects of poison 😢
I like to post spoilers for the stories I find interesting because I don't have much time to read novel due to busy schedule you will find me in most romantic historical manhwa comment sections
