Title: アリョーシャ!, Алëша!, Alyosha!
Author: Kondoh Rururu
Genre: Seinen, Action, Comedy
Serialized in: Shounen Gahosha Young King Ours
Total Volume Count: 1 (ongoing)

Series Summary from MangaUpdates:

Foreign exchange student Alyosha Stalina has been attending a Japanese high school for 3 months. She comes from the nation of Solessia but she is yet to fit in with the other students because of her unfriendly demeanor and cold personality. Rightfully so because Alyosha is a trained assassin that has been murdering people since she was 5 years old. Officials in Estolakia, a country devastated by the attacks from Solessia, found the orphaned Alyosha and trained her as a top notch assassin to work against Solessia.

Her most recent and soon to be last mission is to murder the president of Solessia who is to attend the high school she has infiltrated for 3 months. However, the mission is aborted and she is ordered to remain a student. The only thing Alyosha knows how to do is to be an assassin and has never learned how to be a normal teenage girl. Will Alyosha be able to complete her most difficult mission yet?  

Kenn's Comment: A fun series. Centered around the former child-assassin, Alyosha, as she gets into all sorts of situations in her new life as a Japanese highschool student. The art is pretty good, and comedy is fun and lighthearted. There's an overarching plot to it, however it often takes to the back burner (of the chapter, not the series as a whole; each chapter has a bit of a plot part). If you have some free time, try this one out!