There are still many unknown quantities in solving this problem.

Climbing the mountain road is tough, but the view from the top is worth it.

Walking on the road at night is a bit scary.

He climbed the mountain through the animal trail.

Sadamichi is my best friend.

Sadamichi is my best friend.

Sadamichi is my best friend.

Michiyo is my best friend.

Tsutomu is my best friend.

Tsutomu is my best friend.