It was a surprising NEXT power, they all agreed to it, they had absolutely no idea how it was even possible but that NEXT somehow managed to put Kotetsu in Barnaby's body and Barnaby in Kotetsu's body.
It was confusing.

In the end nothing really changed, it was just Barnaby acting like Kotetsu and Kotetsu acting like Barnaby, their relationship didn't change either, there was still banter back and forth and it was greatly amusing just to hear the tone of their voice slightly changed from the usual. Hearing Barnaby talking so much in such an easy going voice and Kotetsu so little in such a calm voice was definitely a great change and Nathan was fascinated.

"Old man your legs are too long"
"Right now I'm younger"
"It's not because you're in a much younger body that it makes you younger, old man. Though I have to admit your mind is probably 5 years old, and I'm being generous"
"It's a good thing to stay young at heart Bunny!"
"Don't call me Bunny with my own voice, it's creepy"
"Then stop complaining about my body. My body is a good body and in great shape and at least I eat enough. I'm sure you didn't eat any break feast did you? I'm so hungry my stomach hurts"
"You're talking too much, it takes you too much energy"
"It shouldn't! Talking never made oneself hungry. It's unheard of"
"Switching bodies is unheard of too yet we did it. Don't be so quick to draw conclusion Kotetsu-san"

After of while word war everyone started to get really annoyed and when it started to go toward a direction not suitable for underage ears ("I can't believe you have so much curls down there Bunny" "As for you, you have too much hair at all, you should take better care of yourself it's disgusting" "I can't possibly tell them to stop growing" "And you think I decided to have curls down there?") Nathan and Antonio took responsibility and evacuated everyone out of the combat zone.
No matter how fascinated Nathan was even he had his limits.

Thankfully for everyone this NEXT power was limited in time and after two days everything returned to normal. Or nearly.
Because to everyone surprise their relationship became much calmer afterwards, much more respectful of each other.
After getting sunburned in Barnaby's body, Kotetsu started carrying sun lotion for Barnaby in case he forgot, which he now sometimes did on purpose because he knew Kotetsu had some. After falling a few times tangled as Kotetsu because he didn't quite manage to use his legs efficiently, Barnaby stopped teasing him for running in such a embarrassing way.

Their teamwork improved since they now knew each other's weakness, they trusted each other more, and they spent much more time together now that they understood each other better.
That was something everyone could see but Nathan also had the suspicion that they had found a new level of physical intimacy now that they had nothing to hide from each other anymore and spent so much time so close to each other.
Not that they would ever admit it to anyone.