After spending much of your time high in the sky, its always good to take a trip back to the ground. Don't let the grassy plains reminiscent of World 1 fool you, as this course is more akin to a harsh battlefield than a relaxing field. With Bullet Bills and Bob-ombs relentlessly launched in your way, Bowser Jr. is using up all of the Koopa Troop's ordnance to take you down.
Hit the blocks in the beginning for coins, then begin heading right. Going up the hill, you'll pass by a Bob-omb and a Koopa, then come up against a Bill Blaster. Jump over it to the valley below, where you can get a power-up from the blocks. On the other side of the valley is another Bill Blaster, followed by a Bob-omb and a Koopa. Jump across the gap beyond them, then head right to find a Bob-omb and a rotating Bill Blaster.
You should see the first Star Coin on a ledge made out of brick blocks. Break the blocks below, then bounce off a Bullet Bill to obtain it. Alternatively, if you aren't powered-up with a Super Mushroom, knock the Bob-omb to make it blow a gap in the ledge, letting you bounce off another Bullet Bill to get on to the ledge. Once you have the Star Coin, fall down and jump over the gap, being careful of the Bill Blaster on the other side.
Now, you will run across a flat plain with several Bob-ombs marching toward you as well as the occasional Bullet Bill passing by. At the end of the flat plain is a small warp pipe sealed with a brown block. If you have a Mini Mushroom in reserve, knock a Bob-omb next to the block to blow it up, then go Mini to enter the pipe. In the bonus area, you can see a Star Coin, but you can't get it. Jump over the large pipe to your right and hit the block there to make a Mega Mushroom appear. Destroy everything in the room and head left. Stand beside the pipe and move right to force the pipe into the block, letting you drop down and get the Star Coin. Go through the pipe to the right to return to the surface.
If you've just emerged from the bonus area, you might want to backtrack a bit, as the checkpoint is triggered soon after the tiny warp pipe. From there, you must face down two Bill Blasters in front and one behind as you jump on to the blocks over the launchers. This lets you jump over the green pipe and to the other side. You can get a 1-Up from the rightmost block of the L-shaped structure to the right of the pipe, but the Bullet Bills and Bob-omb makes it a dangerous mushroom to collect. Jump over the tall Bill Blaster, then go up the hill and jump over the gap, dodging the Bullet Bills from the rotating blaster on the other side.
Slide down the hill to knock out a Bob-omb and a Koopa, but watch out for the blasters ahead that fire Bullet Bills from two different heights. Go past the block structure and jump over the gap. Avoid or defeat the red Koopa, then jump over the next gap to reach the location of the third Star Coin. This Star Coin is strategically placed between two rotating Bill Blasters, so you'll be under fire while going to grab it. Past the Bill Blasters is a single Banzai Bill Blaster, which fires huge Banzai Bills. You can still jump off of these giant Bullet Bills, which can help you reach the top of the flagpole beyond the blaster.
- The first Star Coin is above a brick block walkway. You must bounce off a Bullet Bill to break the blocks and get on the walkway, or just cause the Bob-omb to explode, leaving a gap for you to jump through.
- There is a mini warp pipe sealed with a single block. Use a Bob-omb to destroy the block and go into the pipe. In the bonus area, go right and hit the block to make a Mega Mushroom appear, then go left and force the pipe above the Star Coin right to obtain the coin.
- This Star Coin is located between two Bullet Bill Launchers. The Bullet Bills are obvious hazards here.
Right before the Banzai Bill Blaster, there is a small hill of brown blocks covering the entrance of a warp pipe in the ground. The lone Bob-omb can't destroy enough blocks to let you access the warp pipe, so you have to get the Bob-omb before it to the right of the rotating Bill Blasters, and use both Bob-ombs to make a large enough hole to reach the pipe. If positioning Bob-ombs while being fired on from all sides is two difficult for you, you can simply use a Mega Mushroom to tear through the blocks. Once the warp pipe entrance is available, go into it to enter a cave. Go right and up the right warp pipe to be taken to the red flagpole.
This secret exit creates a path to World 7-A, just one of several paths to the castle in the convoluted second half of World 7.