Styleing literati bonsai - bunjingi
It's called "Literati" because it was favored among many educated artists such as poets and calligraphers.
Key points to make this shape
1. very thin and long trunk from the bottom to the top
2. has very few branches only at the top of the tree to express old tree. (as if it needed to shed the other branches)
3. doesn't have any branches at lower level of the trunk
4. mainly the balance of the tree locates on the top
5. since the main balance is on the top of the tree, it looks unstable.
6. looks more beautiful if it's slightly slanting to a side than growing straight.
Recommended trees for this shape
red pine, white pine, Japanese plum tree