Tia
Tia and Dekar don't have a relationship per se in Estpolis II. They never have the chance to fight together and really don't talk very much.

Until that famous scene in Parcelyte, that is.

But before that they don't seem to take much notice of each other. When Maxim introduces Tia to Dekar in Bound Kingdom, Dekar doesn't acknowledge her greeting. And despite all of Dekar's heroics that she witnesses, Tia never comments on him at all. In the beginning it's difficult to guess what they make of each other. Most likely, Tia was too busy brooding over Maxim and Selan's growing affections and Dekar was too busy running after Prince Alex and then journeying to defeat Gades.

But when it's all over and the party is in Parcelyte, Dekar sees Tia furtively exiting the city. The look on her face prompted him to start speaking with her, for the first time in the game. As mentioned elsewhere, Tia's broken heart becomes a catalyst for Dekar's character development. As she pours her heart out to him, telling him of the history of her feelings for Maxim, Dekar reveals how great a listener he can be, and how comforting he can be when it's necessary. During Tia's weakest moment, he was respectful and encouraging, and to an extent it helped her cope with things a little better. Typical of such an optimistic character, Dekar came to Tia's rescue because he didn't like seeing anybody upset.

The idea of a Dekar x Tia pairing seems to have a bit of a following in the Estpolis fandom, due to said scenario. However, it doesn't have much potential logically. Tia may have come off as gentle in that scene, but she's actually very pushy. She forces her ideas on others (like her intentions of making Maxim settle down and accept an "ordinary" life), and Dekar wouldn't take to that too well. If he did end up wrapped around Tia's little finger, he'd be very miserable. And if he continued to travel and do battle after the Sinistrals' defeat, Tia would be miserable, too.