My childhood friend is my mate?
Lucy and cobra have been friends since childhood until their village was under attack. And they both went separate ways, Cobra got kidnapped by cultists and Lucy went to fairy tail.
Lucy wasn't at nirvana but she still remembered cobra. At the infinity clock arc she met cobra there. But they were separated by erza. Cobra was determined to find lucy and be more than just friends.
(Okay so if any of you guys have seen Thor: ragnarok, Lucy's eyes are gonna be like Himedal's eyes