I'm not much of a manga fanatic (although I feel like I am slowly becoming one) but there is one series that I stumbled upon and loved reading, and that is Katsuwo's Hitoribocchi no Marumaru Seikatsu. A fun, wholesome manga about a middle school student who has an extreme case of social anxiety, as she prefers to avoid people in general and tenses up when interacting with someone to the point where she vomits. After finding out that her best-and-only friend, Yawara Kai, is attending a different school from hers, she now has to fulfill a promise she made to befriend everyone in her class, or else she and Kai-chan will no longer be on speaking terms.