Sazaesan Syndrome

Mine was quiet and a good one. (adding an "a" sounds more natural)

The lovely characters are popular among us Japanese people. (This sentence is good as it is, but to improve it for the reader it might be better to specify who "us" is as it is could be confusing. Does "us" mean Japanese people, your friends, your family? Who is "us"? I still easily understand from the rest of the entry that you mean "Japanese people")

I also enjoy watching it sometimes. But some of the viewers feel depressed after watching it.-> I also enjoy watching it sometimes, but some of the viewers feel depressed after watching it. (I changed this because in proper written English you should never start a sentance with a prepostion like "But" or "And" as these are used to connect two statements within the same sentance.  It is confusing because in spoken Engish we do it all the time! I hope that makes sense) 

When writing "and" does not follow a comma, however "but" does require a comma:

-I like apple and bananas

-I like apples, but not bananas

I really enjoyed reading your entry! Your English is so good! The corrections I am making are how I correct students in English university! Way to go, very good job!