yet again im stunned by how current life ido is compared to past life ido like what happen...

Spoilers Ahead-
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In this omegaverse, when they bond, they can see each other's memories and feel each other's emotions. Also, pheromone-wise, they are a really good match. Almost "fated pair" kinda thing, but that term hasn't been used in the story. Ido would have fallen for Sejin more in the first life of he wasn't such a douche, and if Sejin hadn't made the mistakes he made. It seems Ido has had his memories of the first life since he was 5, so he's had over 20 years in the second life for those feelings to deepen before they even met.

When Ido bonds with Sejin in the first life, he sees how wrong he was about Sejin. He thought Sejin was a willing participant in using him/his family to better Haesin. Sejin did do things to Ido, like stealing his business info, so Ido had justified reasons not to trust him. After the bond he sees/feels how kind Sejin is and how horribly he's been treated by everyone he's ever come across, including himself. (Mr Kim was the only decent person) How Sejin was used by his "father" and manipulated into doing the things he did. After the attack, he watched Sejin break down for 3 months. He felt everything Sejin felt, let alone his guilt for the brutal SA done by his brother and then himself a few days after. He bonded with Sejin during the SA. He was still in his rut and thought Sejin volunteerily slept with his brother. Attacked Sejin, forcibly bit him, and essentially experienced the assault himself through Sejin's memories. Sejin does kill himself in front of Ido after finding out he's pregnant. He didn't know who's baby it was and couldn't handle given birth to a Kwon child, regardless of who the father was. Ido did find out it was his child.

Thank u for the spoiler (=・ω・=)