She offered me to get me some dry and clean clothes

After the shock wore down I tried to ease the situation by telling her, she could speak Japanese with me. That was the least I could do. After all, it was a bit of my own fault as well. I shouldn't have tapped her from behind (which was never a good idea in Japan, as I remembered now) but should have addressed her politely and face to face. I apologized profusely.
"But first it would be good if I did not have to stand with wet trosers in the middle of the bus."
"Oh ... yes... That... of course ..." The girl took the school bag off the seat so I could sit next to her.
"By the way, I'm Fumiko." she said. "I hope you do not have to go far now?"
"Depends... I live in the dormitories at the top of the park and actually wanted to meet up with two girls in the cafeteria of the Kunimi-Yama, who were so kind as to welcome me there, but I have no idea where exactly the campus is. I arrived in the city only today. Oh... and my name is Robert."
"Oh ... that's bad. Not your name of course. If you go home now, you can't meet the girls, and if you go to the cafeteria with those wet stains on your pants, then you become a laughing stock for half the school. " Fumiko thought hard. Suddenly her face lit up. "I have an idea, you semm to be about the same size as my brother, and I live close by, so what do you think if I take you home with me and lend you some clothes of my brother? ? "