Glossary

Here are a few common Japanese terms and a few game specific terms:-

-chan = suffix indicating feminity (i.e Sarah-chan)
-kun = suffix indicating masculinity (i.e Mark-kun)
-san = suffice indicating title (Miss. Mrs. Ms. Mr.)
-sama = suffix indicating superiority (sometimes translated as Master Nick)
-hime = suffix indicating Princess (this isn't specifically royalty, it turns up in manga/anime by followers to refer to rich heiress')
-ki = suffix indicating formal superiority, but sometimes may be a backhanded insult to indicate aloofness.
-chibi = suffix translated to 'mini'
Kawaii = cute/pretty
Sugoi = awesome/amazing
Honto = really? (e.g. Do you really mean it?)
Sumimasen = Excuse me
Daisuki = Love (big like)
Sensei = Teacher
Aishiteru = Love (this is used a lot in pop culture but this is supposed to be between husbands/wives and parents/children)
(Phrase) Kudasai = (sentence/phrase) Please (e.g can you pass me the butter, please?) [Note: "Kudasai" is always said at the end of the sentence, because of the way the Japanese language is constructed.)
(Domo) Arigatou = (Respectful) Thank you
Gomen (Nasai) = Sorry (formal extension of the phrase)
Ohayo (Gozaimasu) = Good Morning (formal extension of the phrase)
Konnichiwa = Good Day/Hello
Konbanwa = Good Evening
Oyasumi (Nasai) = Good Night (formal extension of the phrase)
Sayonara = Good Bye
Ja matta/ne = See you (later)
Hai = Yes
Iie = No

Student = Player character (PC). There are lots of NPC students, but they are less important.
Report Card = Your character sheet.
Grade = This is how good you are at each subject. It ranges from A+ (Awesome Plus) down to F (Terrible). Human average is D.
Attendance = how many games you have attended. Tracks character growth.
Perk = Something you have, you do or you are, which is generally good for you. Can be a Primary or a Secondary.
Flaw = Something which is generally bad for you. Often an F.
Primary = What you are best at. Often an A or a B.
Secondary = something else you are good at, but not what you are best at. Often a B or a C.