> 1. The kanji based words sound very different from what it would sound like in Chinese
This is because you are probably speaking in mandarin which has deviated a great deal from Middle Chinese ever since the Jurchen Jin conquered northern China.
But if you were to compare it to a more conservative Chinese language like min-nan or some other southern chinese language, the similarities are unmistakable.
美人： Bi Jin (JP) , Bi Jin (minnan), meiren(mandarin)
簡単: Kantan(JP), Kan Tan (minnan), jiandan (mandarin)
時間: JiKan (JP), Si Kan (minnan), shijian (mandarin)
世界: sekai (JP), Sei Kai (minnan), shijie (mandarin)
速度: sokudo (JP), Sok Do (minnan), shudu (mandarin)
確認: kakunin (JP), Kak Nin or Kak Lin (minnan), queren
(mandarin)
区别: ku betsu (JP), ku piat (minnan) , qu bie (mandarian)
人類: jin rui (JP), Jin Lui (minnan), ren lei (mandarin)
and korean:
金 ： Kim (kr), Kim (minnan), Jin (mandarin)
新婦： Sim Pu (kr) , Sim Pu (minnan), Xin fu (mandarin)
學生： hag saeng (kr) , hak seng (minnan), xue sheng
(mandarin)
參加：Cham Ga (kr) , Tsham Ka (minnan), Can Jia (mandarin)
Notice how minnan and korean preserves the ending consonants like "t" and "g" sounds while Japanese simulates the ending consonant with a new character. So the character 速 is pronounced Sok but in Japanese is split into So & Ku where ku simulates the ending consonant.
Mandarin just does away with ending consonants completely. Many other changes such as the lack of the "f" and "v" sound in early middle chinese which is preserved in korean and minnan but not in other Chinese languages where many "b" consonants are converted into "f" consonants. Or the lack of ending "m" consonant in mandarin which is still present in minnan and korean.
This is because you are probably speaking in mandarin which has deviated a great deal from Middle Chinese ever since the Jurchen Jin conquered northern China.
But if you were to compare it to a more conservative Chinese language like min-nan or some other southern chinese language, the similarities are unmistakable.
examples of pronunciation:
忍者: Ninja (JP), Nin-jia (Minnan), Renzhe(mandarin)
美人： Bi Jin (JP) , Bi Jin (minnan), meiren(mandarin)
簡単: Kantan(JP), Kan Tan (minnan), jiandan (mandarin)
時間: JiKan (JP), Si Kan (minnan), shijian (mandarin)
世界: sekai (JP), Sei Kai (minnan), shijie (mandarin)
速度: sokudo (JP), Sok Do (minnan), shudu (mandarin)
確認: kakunin (JP), Kak Nin or Kak Lin (minnan), queren (mandarin)
区别: ku betsu (JP), ku piat (minnan) , qu bie (mandarian)
人類: jin rui (JP), Jin Lui (minnan), ren lei (mandarin)
and korean: 金 ： Kim (kr), Kim (minnan), Jin (mandarin)
新婦： Sim Pu (kr) , Sim Pu (minnan), Xin fu (mandarin)
學生： hag saeng (kr) , hak seng (minnan), xue sheng (mandarin)
參加：Cham Ga (kr) , Tsham Ka (minnan), Can Jia (mandarin)
Notice how minnan and korean preserves the ending consonants like "t" and "g" sounds while Japanese simulates the ending consonant with a new character. So the character 速 is pronounced Sok but in Japanese is split into So & Ku where ku simulates the ending consonant.
Mandarin just does away with ending consonants completely. Many other changes such as the lack of the "f" and "v" sound in early middle chinese which is preserved in korean and minnan but not in other Chinese languages where many "b" consonants are converted into "f" consonants. Or the lack of ending "m" consonant in mandarin which is still present in minnan and korean.