The encounter with Kallen had provided a revelation created by Allen's mana. Once he learned that he could influence the destiny of others, his mana's defense mechanism manifested a means to discern when such influence took effect.
Once he felt an affection for a certain person, he could see a black shadow trying to gnaw at their heart, and that sight made him afraid to interact more deeply with others.
"To get rid of this, I need to get more points," Allen muttered to himself as he stood on the frosty bank of the river and he observed the sirens gracefully navigating the icy waters. Despite the biting cold, he had lingered there for three hours, clad in just a school uniform to shield him from the freezing temperatures.
It was also a place where he used to talk to Felicia, which made his determination even stronger to quickly remove the demonic mana so that those days could return.