Although they took most of their kanji/characters from the Chinese, the Japanese also invented a number of new kanji. Some of them were accepted back into the Chinese character system; others are considered "Japanese only." A quick review of Nelson's JAPANESE-ENGLISH CHARACTER DICTIONARY, which presents 7107 character entries (far beyond the 2000 or so "general-use" kanji) reveals a small number (around 140) of kanji which have a symbol to indicate that they were "made in Japan and not inherited from China" (Nelson:x).
Below are several of the made-in-Japan kanji. Three categories are worth noting. The largest single category denotes particular kinds or species of living things (probably in most cases, species not well known in China, or not important enough to have been given their own character by the Chinese). Another large category of made-in-Japan kanji was devised to denote metric measures such as kilograms, decaliters and centimeters. And another major category denotes a variety of landscape features. A sample is given from each of these categories, along with a sample of miscellaneous kanji.
Japanese and English words come from Nelson. Note that most of these made in Japan kanji are not given Chinese readings. Underlined letters with the Japanese words indicate a lengthened sound.
SPECIES AND KINDS OF LIVING THINGS
awabi: abalone ebi: shrimp, prawn
SETSU, tara: codfish hokke: atka mackerel, lockington
nio: a (little) grebe ikaruga, ikaru: Japanese grosbeak, hawkfinch
shide, shidenoki: a kind of birch tsuga: hemlock, hemlock-spruce
sugi: Japanese cedar sakaki: sacred shinto tree, Cleyera ochnacea
METRIC MEASURES
kirometoru: kilometer senchimetoru: centimeter
kirorittoru: kiloliter hekutorittiru: hectoliter
miriguramu: milligram hekutoguramu: hectogram
LANDSCAPE FEATURES
tao, tawa: col, mountain saddle toge: mountain pass, crisis, crest, climax
nuta: muddy fields yuri: level spot created by sand or dirt deposited by wind or water
mama: steep slope, cliff akutsu: low-lying land
MISCELLANEOUS
soma: timber forest, lumber kashi: mooring pole
masa, masame: straight grained kase: reel, hank, skein
kora(eru): endure, tolerate tsuka(eru): be obstructed, be blocked
tomo: archer's arm protector KO: tie-dying
ama: fisherman, shellfish diver udon: Japanese noodles