You know. When I read this series for the first time, I got bored. Something felt missing, so I did not finish the first season. When the second season started I kept receiving the notifications so eventually I skimmed through the chapters and the whole dragon thing caught my attention, therefore, I read the second season properly and I liked it. That made me go back to the first season and read it completely. It was the best decision because everything made more sense and was way more enjoyable, I could understand Sol's feelings and actions better. Ryan's existence gave meaning to the whole story for me.
My favorite manhua (Devil Wants to Hug) deals with reincarnation and the point is, you can't hate the past life after all the sacrifices they made, both deserve to be happy and it is possible. (I hope to make sense, not my first language).
Still blows my mind that some of you are reducing this to "Ian good so Brian bad, I like Ian so I must hate / disrespect Brian."
Like it or not, Brian is the entire reason why Sol is how he is, is the reason why the world is as it is, and is the reason why Ian can meet Sol in this life. Brian's life was bittersweet but his sacrifice has rippled across the entirety of this universe in ways that are undeniable.
He's a great protagonist and you are selling this story short and the complexity of the author's intentions when you say "lol I didn't reason the second season because I hateeeeee Brian and loveee Ian give me a summary of what happened!" Nothing he or the author could do would have ever changed your minds to feel otherwise because you never gave him a chance to begin with.