YOU SAID:
Happy Birthday, my friend!
INTO JAPANESE
友達よ、お誕生日おめでとう!
BACK INTO ENGLISH
Friends, Happy Birthday!
INTO JAPANESE
お友達、誕生日おめでとう!
BACK INTO ENGLISH
Happy birthday to your friends!
INTO JAPANESE
お友達への誕生日おめでとう!
BACK INTO ENGLISH
Happy birthday to your friends!
That didn't even make that much sense in English.