If Tsunade kisses Naruto, it could strengthen their relationship in a mentor - like way. Naruto might see it as a sign of deep respect and trust from Tsunade. He would likely feel more confident in following her guidance. For Tsunade, it could be a way of showing her pride in Naruto's growth.
One great Tsunade and Sakura fanfic I read focused on their mentor - mentee relationship. It showed how Tsunade passed on her medical ninjutsu skills to Sakura. The fanfic also added some interesting side stories about their adventures together in the Hidden Leaf Village.
Naruto might be initially confused. He trusts Tsunade, so being kidnapped by her would be completely unexpected. He would probably start by asking her why she's doing this.
The relationship between Naruto and Tsunade could be strained. Other villagers might notice the tension, and it could affect the overall morale of the village. Some might side with Naruto, thinking Tsunade is being too harsh, while others might understand Tsunade's pain and disappointment.
Perhaps a shared experience like fighting a common enemy could bring them closer. If they are in a battle together and Naruto saves Tsunade's life, or vice versa, it could be the start of a deeper emotional connection. Tsunade might then open up about her family to Naruto, and Naruto could share his own feelings about family, as he has always longed for one.
Tsunade would probably be very suspicious at first. Naruto suddenly appearing from the future? It's not something that happens every day. She might think it's some kind of enemy's trick or a genjutsu.
Tsunade would probably be shocked at first. Naruto is like family to her. She might immediately refuse and try to talk some sense into him. She could say something like 'Naruto, you're stronger than this. There's always a solution to every problem.'
In many fanfictions, Naruto's determination and positive attitude start to rub off on Tsunade. She has been through a lot and is a bit jaded, but Naruto's energy makes her feel alive again. This new - found connection leads to a budding romantic relationship. For example, Naruto might bring her small gifts from his travels, which are simple but meaningful gestures that slowly warm Tsunade's heart.
It could be due to the current situation in the village. There might be threats that required Naruto to stay. Tsunade, as the Hokage, had to consider the overall safety and stability of the village. So, she denied Naruto's request for the training trip to ensure he was available in case of any emergency.