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My good sir, this is Makoto Kikuchi from Idolm@ster, a series of video games based around raising idols to be a popstar in Japan.
You have selected Makoto Kikuchi, vers. 2. This is her design from the most recent game.
Her pictures can be found on danbooru with the tag kikuchi_makoto. The artist who drew your two pictures is called nekopuchi. Searching his tag on danbooru will give you multiple pictures of Makoto along wiht other characters. I'll dump my Makoto collection for you.