Pride
Having pride for himself he could understand, but feeling pride for someone else was a bit confusing to Sai. But here he was, smiling as she kicked the ass of an older Ninja who had insinuated that has a medical-nin she couldn't fight as well as the others. While Naruto may have taught him that friendship is one of the most important things a man can have, Sakura had taught him that you should never underestimate a woman. He could think of no better example than what he was witnessing currently. The blonde woman's eyes were narrowed and there was a dark aura around her as she focused on the fight she was in. He was certain that nothing could break her focus at the moment, she was locked in on her opponent and he was all that she saw. Even though he really had no connection to Ino other than a friend, he felt so proud of her as she proved that she was a force to be reckoned with.
"Still think I'm weak!?" she shouted at the foolish ninja who had made the mistake of underestimating her. The woman was currently standing behind her opponent, she tapped her sparring weapon on the top of his spinal chord. Defeat.
"How-" the man started, turning around in shock as the blonde glared at him.
"You know you really shouldn't disrespect medical-nin. The next time you need someone to save your life I might not be so accommodating" she almost spat. He could tell she was still furious, it was no secret that she was a little touchy about the fact that she wasn't as strong as some of her former classmates.
To Sai it didn't matter. The woman was brilliant with her mind and that was a weapon all in itself. When he watched her fight he could see the calculation in her eyes as she plotted her next move. She was just as brilliant by herself as she was in a team situation.
"What the heck-" a voice sounded behind him. Naruto stood with his mouth dropped open at the sight of the demolished training room. He seemed to be grappling for the right words for a while before he finally stepped up next to Sai and spoke to him
"What the heck happened here?" He managed. Usually if there was any destruction it was left by Naruto himself, so he was surprised to see a mess that he had no part in.
"Don't underestimate medical-nin" Sai summarized for his friend. Naruto just nodded dumbly, still staring at the wreckage.
"Well I'm going to get out of here before someone thinks I did this" the man in the orange jumpsuit says as he turns and exits just as quickly as he had entered.
Sai still couldn't shake the pride.
Thats right
he thought
Nobody underestimates my girl