Despite their rocky beginning, there are many, many instances throughout the manga that show just how comfortable they are with one another - on a physical and emotional level. This is especially obvious whenever Ranma uses his cat-fu. This is when he's at his most vulnerable, yet the only person who can calm his down, who he trusts implicitly, is Akane. It also shows clear progression: At first, Akane acts shocked and a little upset when he lands on her lap, especially in front of their classmates. But quite a few chapters later, when Ranma's battling Cologne, Akane eventually embraces this new role, and even goes so far as to call him over ("here, kitty, kitty"), even reaching her arms out to catch him. She doesn't act annoyed, inconvenienced, or upset - despite this all happening, again, in public. She's simply supportive and reassuring, a definite change from her initial reaction at her school.

There is also an easy camaraderie between the two of them: They're constantly spending time together even when they don't have to, and after battles, Akane's always quick to dress his injuries. For two people who are both so stubborn, who claim not to like each other, their actions always prove otherwise. And again, you can see the progression. In the beginning, they're determined to keep their distance and can't stand to be seen together, but it isn't long before they naturally sit next to each other at meals, comfort each other, and even work together when they don't have to. They even share physical touch, like when Akane takes Ranma's hand before asking him to stop training in her bedroom (right before punching him lol), or when Ranma shyly takes her hand after Ryugenzawa.

     

This effortless camaraderie is especially apparent in the manga chapters towards the end (Chapter 309-311) when they stalk Nabiki to prevent her from bankrupting their house. In that story, their reactions to her crazy spending habits and cutthroat dating style are hilariously in synch, proving they have similar morals and beliefs, and that they really are on the same wavelength when they're working together and not fighting. Plus, just look at how closely they sit; they're always in each other's personal space.

This can also be seen in the Miss. Hinako fighting fish chapters (316 - 317) when they try to help their teacher tutor Ranma. This is a great example of how "normal" and healthy  their relationship can be outside of all the messy, pushy suitors and insane martial art challenges. They've proven they can be caring and supportive of each other, and that they value each other's opinion. That never would have been possible if their relationship hadn't grown from the awkward forced affair it was in the beginning.