@ Dreamy
DALDO is a more suited than MIJI.
SDM is not a clueless girl. She is a leader, strong, motivated, persevering. She does not need someone to help her. She needs someone to understand her, support her, give her strength to overcome the difficulties, give her a hug when she needs it. She has this delusion of an ideal first love but she is no romantic little girl actually. She is a fighter who will do the most with a good guide and a good man next to her.
NDS is a considerate guy. He pays attentions to be good to his family his father or his cousin, his friends even strangers. He wants them to not be hurt and not misunderstand. He is better suited with Dal Mi. He tries to understand her and be the emotional support she needs. His warmth and caring side is what will help Dal Mi in her development.
HJP is a great guy. He is competent, ruthless in business. He has a fun and friendly appearance in private but he has no real friends. He is a solitary guy who cares to be fair and not indebted to anyone. He will be a great mentor for Samsan tech but his personality is not matching Dal Mi's one for me. He does not have the warm personality she needs.
Now we will probably see a love triangle since these three will work together and get closer to each other. It is said love is also a matter of timing. Dal Mi and Do San are in the right timing. Fate brought them together at the right moment to start a journey together. Ji Pyeong missed his chance the day she told him not to follow her and he let her slip away.
Btw, Ji Pyeong did not made Do San become the Do San of the letters. Do San made himself this guy. After he met her eyes in the park and read her letters. Do San cut the girls who came to him now he is the one who went to her. He went there by himself.