If the trunk grows up at an angle, due to being exposed to a wind coming from one direction or other obstacle, and the tree is growing in one direction on an angle from the base to the core, this is called Shakan style bonsai.
一方向からの風に晒されていたり、障害物などがあるために根元から斜めに立ち上がり、樹芯にかけて一方向に傾いた樹形を斜幹と呼ぶ。