Kannagi

Chapter 27 : In The First Year Of High School, We Only Have This One Summer Vacation
Chapter 26 : Hakua's Castle 2
Chapter 28 : The End Of Summer
Chapter 26 : Hakua's Castle 2
Chapter 28 : The End Of Summer
Our unlucky protagonist, Jin, uses the trunk of a sacred tree to carve a statue for a school project. When he takes it outside, to his surprise it begins absorbing the surrounding earth and transforms into, hold your breath on this one, a girl! So like all similar setups this guardian deity is pretty pissed that her tree was cut down and lives with Jin while she takes out her anger on squashing bugs....er, cleaning the "Impurities". Kannagi has also a "deformed" version named Kanpachi and was created by the original author's brother. It's worth a look.