Frisk remained kneeling on the ground. She worked her jaw in anticipation as she watched the two skeletons. In that moment, she would give anything for real fighting experience. Even if it was just extra HP, she could still stand alongside Sans. That was the downside of a pacifist route, she supposed. If things got too rough, she couldn't really protect herself. Then again, there weren't any monsters in their Underground like that Sans. Even at max HP, Frisk doubted she'd be much of a match for him. 

Kneeling like that on the sidelines, Frisk felt completely useless. She rocked back onto her toes and shifted nervously. The fight had suddenly stopped, and all she could do was cautiously watch the unstable Sans. When he suddenly elected to end their fight there, Frisk let out a shaky breath of relief. She lowered her head and let her stiff neck and shoulders relax the faintest bit. 

Her attention went down to the ground, yet her head quickly snapped back up when she heard her Sans shout. She looked on in horror as he moved to follow the other Sans into that strange void. She moved to get up, yet stumbled and collapsed back to the ground. She passively wondered how much HP she had lost, but her main attention was on her dear friend.

"Sans don't!" She reached out for him, fully expecting to see him disappear into whatever that place was. When he didn't, she let herself relax her arm but didn't relax fully. Concern for him pushed her to successfully stand. 

"Sans?" She approached him gingerly, out of fear that she might startle him. She didn't understand a word he said, and that just made her worry more. Watching him closely, she saw him move his hand. It didn't take her long to realize that he was going to put his hand in his pocket...Which wasn't there. She looked down at herself and realized that she had been wearing his jacket the whole time. Quickly, she shrugged it off and put it around his shoulders.

"It's okay," she softly said. Her hands remained on his shoulders, though their grip was light in case Sans wanted his space. 

She tried to keep her strength, she really did. But she couldn't keep herself from leaning against him, relieved that he was still there and not a pile of dust. She nuzzled softly at his head.