
I got this information from someone who read the novel and copied and pasted someone’s telling the entire story. So here you go. SPOILERS!!
“Dohyun does know that wooyeon is the kid he used to tutor. He knew from the moment he met him in chapter two. he decides to approach their relationship different this time around because when he was hired to be wooyeon’s tutor, it was to report information to his mother.
Dohyun was abandoned at eight years old and since then, has had the mindset of using others to excel. The first time he does this is through wooyeon’s mom, which is how they know each other in the first place. Wooyeon’s mom finds him an adoptive family and when he enters university, she asks him to tutor wooyeon.
Dohyun was very nice to wooyeon, and we later find out that he genuinely cared for him during their time together. dohyun was so used to being wanted on a superficial level, and wooyeon provided him a more authentic connection. this does lead him to leave for the military though, because at this point wooyeon is 14 and he is
Dohyun decides to approach their relationship differently this time around and it is when he figures out that his feelings for wooyeon are romantic that soohyang (wooyeon’s mom) calls him up and basically guilt-trips him into telling wooyeon the truth. here is where i think dohyun messed up. a
Dohyun doesn’t tell wooyeon the truth until they are together and have already had sex. it deeply hurts wooyeon (understandably) and then the rest of the novel is dohyun asking for forgiveness and them getting back together.”

The ages are said to be Dohyun was 20, Wooyeon was 16. As both Dohyun and Wooyeon clarify it, but ig it depends on if you want to stick to what they said in Korean age or international age.
Dohyun didn’t like him romantically at that time. He genuinely care and worried about him, found out that Wooyeon had a crush on him, then felt flattered by it. But he realized that it wasn’t appropriate to think that way, so he left. It’s the natural feeling when you hear someone has a crush on you, even if you don’t like them back- it may feel nice like a compliment. But Dohyun clearly understood the age gap and thought it wasn’t good to think that way, as well as his position as a tutor, even if he didn’t reciprocate those feelings romantically.
Can someone spoil me why the ml is manipulative?