I wonder the sane as Takanori-san. If you want to reply to your Japanese friend in Japanese, I need to know if you'd like to use the formal form or informal/friendly form.

Do you want to write English or Japanese ? If you want English correction , you had better ask English native. Or are you asking how Japanese feel the message ?

Thanks for coming to Japan And I want to say something like; You thanking me is rediculous. I should be the one thanking you. Thank you for always being so nice to me and thank you for helping me as well as making me smile. .................... I really enjoyed my trip to Japan. Thank you so much for spending time with me and being so nice. I really appreciated your help. You made me smile!