Isn't That Esper My Childhood Friend?

Na-on, an S-class guide affiliated with the Central Center. There's a consistently tiresome question he's heard regardless of the passage of time. "What's really going on between you and Esper Kang Ah-jeong?" Esper Kang Ah-jeong, one of only three S-class espers in the country. Perhaps it's because they were childhood friends and he's her exclusive guide. To the tiresome question, Na-on could answer emotionlessly, like a vending machine dispensing canned drinks at the push of a button. "We're like brothers. We've seen everything there is to see since we were kids." But one day, after coming back from the brink of death, Kang Ah-jeong says... "What is it? Do I need to prepare myself? Is...