You see a thread-covered hill, but it's all lumpy and weird. You approach it to take a closer look, and you see it's actually a huge net with a bunch of stuff caught in it: fish, cats, tree branches. All this random stuff is what's making the net look so lumpy!

This net is creating a serious obstacle to you mowing (もう) the grass, which is what you originally came here to do. For now, you're just going to have to mow around the net, since it has way too much stuff in it for you to be able to drag it away.