Goishi Hiroi, also known as Hiroimono, is a binary-determination logic puzzle.
Goishi Hiroi Wikipedia
Goishi Hiroi is played on a rectangular grid in which circles appear at some of the intersections on the grid.
The object is to conceptually claim the circles from the grid, as though they were stones on a board. Starting with a stone, continue in any orthogonal direction until an unclaimed stone is reached. Repeat until all stones are claimed. Once a solution is found, number the stones in the order required to claim them all. You may not skip over unclaimed stones, although you may skip over empty spaces or claimed stones.
A good starting point is to find a stone which is only reachable by one other stone. From there, much of the solution will become obvious. The most important skill in Goishi Hiroi is remembering which stones are claimed and which are unclaimed.