i'm assuming by "ken" you mean a name because ken in Japanese has a few meanings such as prefecture etc. names in Japanese are not written in kanji, theyre written in katakana, which are specially designed for English and other foreign languages. you would write it like this: ケン :)
We write it as 鯉[koi] in kanji in Japanese.
君子の件, although there're a lot of kanji for "Ken".. If what you want to say is "The virtuous man's discipline" it's: 君子の拳
There is no Kanji for "madsam."
沖縄県 (okinawa-ken), which is "Okinawa Prefecture", omitting the last Kanji 県 (ken) makes it 沖縄 (okinawa).
you can't
Earthquake in kanji is written as 地震.
龍 or 竜
'Ojiichan' written with kanji isお祖父ちゃん.
you don't its written in katagana
櫻.
you don't its written in katagana
酒 is the Kanji for sake.