Considering blonde guy(Larkan) didn't fully learn how to act human and care for them the same way Sol did, he prob went for the drastic measures because he took to literally what Brian and Sol told him. Sol told him that his love for Brian was something he has learnt after he lost everything. While Brian told him he chose to prioritize Sol's decision over what he wants because Sol abandoned everything to be with him aka Larkan might have thought he just have to do that to win Brian too in his next life.
Despite 900 years have passed seems like Larkan never crossed the line with any humans thus he never fully learnt to consider and care for them. At the same time because of it he never fancied the idea of courting Ian. He mostly see Ian as a possession or a pet he deeply love. So even Larkan did imprint himself on Ian due to their relationship that can't equal the "love" between Ian/Sol, in the end it was all for nothing. Also due to Larkan not really caring for humans, he also extremely closed minded. For centuries he only considered Brian that gave birth to his misconception that Brian is the only person worth having around which in the end caused the obsession too.
...i got a bit of theory.
Considering blonde guy(Larkan) didn't fully learn how to act human and care for them the same way Sol did, he prob went for the drastic measures because he took to literally what Brian and Sol told him. Sol told him that his love for Brian was something he has learnt after he lost everything. While Brian told him he chose to prioritize Sol's decision over what he wants because Sol abandoned everything to be with him aka Larkan might have thought he just have to do that to win Brian too in his next life.
Despite 900 years have passed seems like Larkan never crossed the line with any humans thus he never fully learnt to consider and care for them. At the same time because of it he never fancied the idea of courting Ian. He mostly see Ian as a possession or a pet he deeply love. So even Larkan did imprint himself on Ian due to their relationship that can't equal the "love" between Ian/Sol, in the end it was all for nothing.
Also due to Larkan not really caring for humans, he also extremely closed minded. For centuries he only considered Brian that gave birth to his misconception that Brian is the only person worth having around which in the end caused the obsession too.