”GOMEN"/"GOMEN-NASAI" and "SUMIMASEN" are actually used in the same case and same meaning.

However, original meanings are different.

”GOMEN"/"GOMEN-NASAI" means "forgive me". But "SUMIMASEN" has more deep meaning.

In the daily life, Japanese people are giving and receiving "respect" each other in every human relation and checking their "Balance Sheet of respect" in every action.Remember that the "respect" can be sometimes minus value.

Then, when a Japanese receives respect larger than he/she gave, he/she feel guilty with the too much respect he/she received. "SUMIMASEN" means "the returning (respect) does not reach the end" or "I can not give you the respect to compensate what I made".

"OIKUTSU DESUKA?" also can be used when one buy something.

"O-MOCHI WO KUDASAI:Give me the MOCHI please"
"O-IKUTSU DESUKA?:How many MOCHIs do you need?"

I will be confused when asked "OIKUTSU DESUKA?" suddenly. "NAN-SAI DESUKA?" can not confuse the listener.

Thank you so much guys! Thanks a lot for the explanation. :pinkbow:

Hey guys! I've been told to introduce myself here :D Nice to meet you all!

My name is kito :D

I am from Australia!

And I was born in December 26, 1998

I have a wide range of interests from sports to gaming! I am also an youtuber that enjoys making content about anime, manga, japan and related news :D. Feel free to check it out! https://www.youtube.com/kitosenpai

I hope we get along :D

Hello Kito nice to meet you :)
I hope you'll enjoy your staying here.
Welcome to Japan forum :)

Hi from Italy
 

Hi I'm Joe from Italy, I'm interesting in Japanese Art and Culture, I practice martial arts and I'd like to know everything about Japan!

Hi my name is Philip I am new here nice to meet you all :D

yoroshiku onegaishimasu
 

ohayo gozaimasu minna san! watashi wa ana desu. i'm from romania, dracula's country and i've discovered japanese anime since i was a child with Hello! Sandybell. for just about 2 years i started watching some new animes and discovered japanese mangas. since then i've been addicted in watching and reading animes/manga, especially those that are related with school, romance, slice of life.
i'm an adult according to my birth but i think i'm still a child inside and hope i will never change.
i thought i should join this forum because i had some questions over the time regarding animes and manga and i had nobody to discuss them with. sharing a great experience with somebody else makes it even more enjoyable right?

so nice to meet you all and hope we will get along well!
yoroshiku onegaishimasu!!!