Mario wakes up in a dark world. Someone says hi and asks if it's his first time in The Underwhere. It's a joke, as people don't arrive here twice. Mario asks what this place is and the Shayde says it's where people go when their game is over. It's also called World -1. The Shayde asks how Mario's game ended, but Mario says his game's not over. The Shayde says he's in denial and that he'll hear the truth from Queen Jaydes, the scariest person in The Underwhere, who rules over the Shaydes. None of the Pixls are with you, nor Bowser or Peach, but you still have your items. Walk to the right to find a fountain. Stand in it to fully restore your health. To the right is a Save Block and a door.
Go through the door and someone hums to themselves. It's an angel-like being, speaking in an older version of English, wondering if she'll meet her most special someone today. She believes it will be a prince of fair countenance who is pining to meet her. She commands him to fly to her. She looks at Mario and scowls, asking why he's staring at her. He didn't hear her pine for an old, mustached fatty and tells him to be gone. In the area are tall pipes and spikes. Flip to get around them, but you'll have to keep switching between the front path and the back path. At the end is a tall pipe. Flip to find a flip block so you can reach the Super Shroom Shake on top of the pipe. Go through the door.
There's a wide river and a boat. You can pay money to cross the river, the River Twygz, or just swim across. Avoid the hands in the water, which are called Underhands. They can't be defeated and will hurt you. Go through the door on the other side of the river to reach a palace. One of the Shaydes says that Mario should talk to Queen Jaydes, who knows all the bad things everyone's done in life. If a person was good, they get to go to The Overthere. If not, they'll suffer in The Underwhere. Talk to Queen Jaydes, the mistress of The Underwhere. She's the ruler of those with ended games and weighs the sins from one's time among the living. If they're light enough, one gets to experience the bliss of The Overthere. She senses a strange energy and asks if Mario brought anything strange into The Underwhere. Mario hands her the Pure Heart and she is shocked. It is badly damaged. She wonders who Mario is to have it and asks what happened. She then gets a call from Grambi, saying that Luvbi is missing. She and her D-Men are already shorthanded, so she asks Mario's help to find Luvbi, a Nimbi who vanished. Agree to help and she'll take the Pure Heart, promising to return it when he returns with Luvbi. She gives Mario a Door Key, saying a strange fellow dressed in green fell into the River Twygz, who definitely is not Luvbi. She says to check there first anyone and says the key opens the door to the underground waterways.
Drop down into the River Twygz and avoid the Underhands. Flip at the bottom to find a hole that leads to a locked door. Unlock it. Swim up and over the ledge and push a block down to the right. Drop down and throw the switch to drain the water. Go up and right to find some brick blocks. Break them, then throw the switch again to fill the area with water. Swim up and to the right. Flip to find a path out of the area. Flip to reach a block and push it down to the left. Drop down and throw the switch to drain the water. Hit the brick block for a ladder. Flip to find a path out of the area. Go through the pipe and flip for some coins. Go through the door to the right and drop down. Flip and go back to find a hidden chest with a Dry Bones card. Climb up the fountains to the right to find someone groaning. Mr. L's music starts playing. It's a man in a green cap, wondering how he ended up in this lousy place. He remembers being grabbed by Count Bleck's underlings. He wants someone to help him. Mario greets him and Luigi freaks out. He remembers his brother and missed him a lot. He asks why Mario's here, saying he doesn't know where he is. Mario explains and Luigi can't believe he's in the land of ended games. He thinks Count Bleck's baddies did him in like they did in Mario. He takes it well, saying everyone runs out of extra lives. He wonders what to do and Mario explains he's looking for Luvbi. Luigi agrees, saying he has lots of free time now that his game is over. He joins the party. Hold Down on the Control Pad, then release to do a Super Jump to reach high ledges and attack enemies. Luigi wants to jump for joy. Flip to find a Long-Last Shroom Shake in the corner, then Super Jump to reach the door.
Use the Super Jump to quickly go through the waterways, then head to the left after getting out of the River Twygz. Super Jump over the pipes until you reach the door, then Super Jump on the pipes to the left of the door, without going through it. There are Ice Piranhas here, as well as a Poison Cherbil. In the high item block, you'll find a Happy Flower. Just to the right is a tall pipe with an Ice Piranha. It leads to the background. Go through the other pipe in the background to reach a pipe in the background below. Go through the other pipe in the area and it takes you to a room with a Gigabyte, a flying skull that will only take 1 HP of damage per hit. It has 6 HP and will give you many coins when you defeat it. Defeating it will also make a chest with the Peach (3) card appear. Return to the foreground and go through the door. You'll hear the angel-like creature humming again. Flip to get past the pipes with the Ice Piranhas and talk to her. She tells her sweet prince to hasten to her. She sees the Mario bros, and calls them aging men of mustache. She asks what they want and they explain they came to find her. She refuses to consort with such hairy faces and wants only princes to approach her. She asks if they claim to be her prince, and if so, they should know her name. Tell her her name is Luvbi and she taunts them, but is shocked when they know her name. The thought of them being her prince can't be abided and she won't date a man so old and unpleasant to the eye. She decides to return to her mother.
Return to Queen Jaydes and Luvbi says the foul, hairy creatures return at last. She calls them liars as they weren't princes, but found her at the request of her mother. Queen Jaydes tells Luvbi to mind her manners and says she sent them because she wandered off without permission. She tells her to apologize and Luvbi says she is sorry that the Mario Bros are so hairy. Queen Jaydes says Luvbi had them worried. She gives back the purple Pure Heart, fully restored, as a sign of gratitude. She has power over life and death, so she restored the Pure Heart. She says the fact that the Pure Heart survived means fate is on their side. She also explains that Mario's and Luigi's games are not truly over and they were sent to The Underwhere alive. She can allow them to return. She chants her name, then Game Over several times, then Continue.
The bros end up on Flipside Tower. Tippi says Mario is alive and Merlon was sure Mario's game had ended, but is marveled that he is truly alive. Luigi says his bro bounces back and that he bounces, too. Back in Merlon's house, Luigi introduces himself as his bro's bro. Tippi asks if they've met before, but Luigi doesn't remember. Tippi thinks he may be the fourth hero. The Light Prognosticus says the seventh Pure Heart will draw together two men and its brilliance will shine on the way to the last hero. Tippi says she never stopped believing Mario would return and asks about Peach and Bowser, thinking they could come back as well. She says to find the next Heart Pillar.
Go to the B1 Flopside Outskirts. Use the Super Jump to jump onto the tall wall, then flip. Drop down to the back to find a chest with a Piccolo card. On the other side of the wall on the front side is the Heart Pillar. Place the Pure Hear to make the purple door appear. Tippi says they must act quickly to stop Blumiere. She then wonders who Blumiere is.