I'm looking for a manga series with themes that deal with foreigners in a new country, outcasts of society and/or segregation/racism. Basically, any manga that deal with the issue of "people not being accepted." The reason of them not being accepted doesn't matter, and this theme doesn't have to be the focus of the manga.
here are some examples I have thought of:
One Piece - Chopper being rejected by both reindeer and humans because of his appearances before meeting the Strawhats.
One Piece - segregation between fishmen and humans
Naruto - Naruto being rejected by members of the Leaf because he was born "cursed" by Nine-Tails.
Bleach - Ichigo being called a delinquent because of his foreigner-like hair
China Girl - a short seinen romance, a guy obsessed with a young woman from China living in Japan and slowly coming to realize what she faces as an immigrant.
Fruits Basket - Excellent shoujo fantasy series about a family cursed by the members of the Chinese zodiac to transform into their respective animal when embraced by any uncursed member of the opposite sex.
Kaguya Hime (Reiko Shimizu) - Er, not sure how to summarize this - it's beautiful and striking and extremely complicated. But the contrast between humans and the moon people of the original Kaguya-hime legend plays a big role, as does being outcast among one's own kind.
Most series by Hwang Ri Mi covers the theme, by being a modern teen lost in history or a gangster among ones school.
Otoyomegatari / A Bride's Story - Also covers overlapping sets of inside/outside, in various gentle and violent cycles, many but not all relating to the dubious status of women who are and are not wives in 19th century central Asia. (It's also even more beautiful to look at than Kaguya Hime.)
Amakusa 1637 - A handful of modern teens, most of them actually Catholic, are sent back in time to Amakusa just before the revolt and very bloody suppression of Christians in 1637. Less of this is scanned than you might like, though.
That should be enough for now.