Don't know if either of these count, but here we go
3. Baek Seung Soo and Lee Je Hoon from Hot Stove League - Whenever their characters were on screen together I felt this palpable tension between them. The romantic relationships aspect was never touched upon in Hot Stove League, but I just felt like they would make a great couple.
4. Oh Kyung Soo and Santa from Inspector Koo - I love those relationships with banter and little arguments, and these two had just that. There was an actual LGBTQ couple in this series, but all through the episodes, all I could think about was that they had chemistry too.