"Stupid Dad. Stupid coin. Stupid ghosts." Bowser Jr. Grumbled as he marched through the old wooden halls. It was a last minute task, but Bowser had sent his son out to the ghost house on Donut Plains, to retrieve a rare coin he had dropped there earlier in the week. With a small satchel strung over his shoulder, he searched high and low for the missing treasure. The Boo infested mansions sprinkled through the Mushroom Kingdom always gave him the creeps. Sure, they had Boos serving in the castle, but the ones in the houses were more "wild." An encounter with a ghost house Boo could go in either a good or bad direction, even for a koopa. 

"Ah ha!" He exclaimed, seeing the coin in the far corner of the mansion's furthest back room. Picking it up, he placed it in his bag, and turned for the door. 
"Ack!" He shouted, as a large Boo rose out of the floor in front of him. It was far from being a king, but it was still twice the size as the young koopa's entire body. "H…hey there Mr. Boo," he stuttered nervously. "I was just leaving, ok?" 

The Boo moved closer, a devilish grin across its face. Junior nervously took a step back, his shell clunking against the wall. The Boo floated closer and stuck out its tongue. 

"L…look, I don't want any trouble. I was just here to grab something my Dad lost." Waving his hands in front of him, Junior winced as the Boo moved even closer. Now just inches from his face, the ghost slowly descended out of the young koopa's sight. Fearfully frozen, Junior just waited, worried about what the spirit was going to do. 

SLUUUURP! 

"Wha!?" Junior yelped, jumping in place. The Boo's long ghostly tongue had licked from his crotch, all the way up to his lower chest. It had a surprisingly wet and corporeal saliva, which dripped down the koopa's body. Now with eyes wide, he looked at the Boo which floated again near his face.
"Wait, you couldn't possibly…"

The Boo cackled and vanished into thin air for a moment. Junior was stunned. He didn't think the ghosts of the Mushroom Kingdom had any interest in such things. It wasn’t like they could actually procreate in any capacity…right? Though he began to wonder if conscious desires for intimacy would perpetuate after death. Turning visible again the Boo seemed to want a response of some kind. 

Slumping the bag off of his shoulder, Junior widened his stance a little. "I guess I don't have to go back right away. You do know I'm a boy right?" 
The Boo cackled again but remained visible. 
"O…ok then Mr. Boo. Go ahead and do your thing." Junior was nervous, but figured he didn't have much choice. Doing his best to stay calm, he took a deep breath and let the ghost continue. 

The Boo floated down again and licked as it did before a few more times. Each time it crossed Junior's slit, the young koopa let out a soft moan, indicating to the ghost where to focus its tongue. Junior, not able to place his hands on the Boo's form, instead spread his arms out and braced himself on the wall. After the fifth lick Junior's tapering member finally peaked out of his slit. The Boo now focused its tongue on the young koopa's length which grew to an impressive 6 and a half inches. It cupped its tongue beneath Junior's cock, rolling the squishy red boyhood back and forth. 

"Ah. Ah. Ah," Junior panted, feeling every motion of the Boo's tongue. The ghost sensing that the young koopa was enjoying himself, stuck its tongue out further and pulled up. The Boo floated upward, the tip of its tongue now caressing Junior's tail, and lifted him into the air. 
"W…whoa! Hey Mr. Boo. Whatcha doin'?"

The Boo cackled and wiggled its tongue. As it continued rubbing against the young koopa's cock, it pressed the tip against his tailhole. Junior gasped as he realized what the ghost was trying to do. 

"Wait, not back th…AAAGH!" Without giving Junior time to fully respond, the Boo plunged its tongue deep into the young koopa's tailhole. He was now being pleasured by the firm lower third of the ghost's tongue from the front and deeply rimmed from the back. All Junior could do was let out a long moan and let the Boo have its way with him.
This wasn't exactly what he expected to be doing today, but as the Boo worked its tongue he couldn't help but become thankful for the assignment. Up. Down. In. Out. Somehow the Boo was an expert at pleasuring a male koopa. Junior, despite feeling amazing, couldn't help but wonder if the Boo was originally male or female. Though only just starting puberty recently, he had already taken a liking to other boys as well as girls. By his calculation it didn't matter what the Boo was, but he was still curious all the same. That curiosity wouldn't last long however, as a familiar feeling began developing in his lower body. 

SHLUCK SHLUCK SHLUCK SHLUCK 

The Boo squished Junior's cock against his body, as the tip of its wet ghostly tongue pumped in and out of the young koopa's tailhole. Now floating in the air with the ghost, Junior was at the edge of infinite pleasure. 
"Ah, yes!" He shouted, his toes curling tight. "Here it comes!" 
Clenching his fists, the young koopa released his seed into the air. It flew upward and came splashing down onto the ghost's tongue. As soon as the Boo got its first taste of Junior's cum, it pulled out of his tailhole and opened its mouth wide. Bowser Jr. was surprised to see that the liquid didn't fall to the floor through the specter, but instead it vanished on its tongue and into its mouth. 
His cock continued throbbing, shooting out one of his biggest loads ever. Lost in the pleasure of having his sensitive member licked clean, the young koopa let out a sigh of relief with the last of his cum vanishing into the Ghost. 

Slowly the Boo floated back down, and let Junior rest on the floor. It cackled one last time before fading into the darkness. The young koopa remained on the floor for some time following his climax. His breath was heavy as his cock slowly receded back into his slit. 
"Stupid ghost," he muttered to himself, reaching for his bag. Sitting up he pulled it over his shoulder and sighed. 
"Hey are you even still here!?" He shouted into the darkness. Grumbling, he stood up and headed for the doorway. Stumbling a little as he walked, it was clear the Boo had done a number on his tailhole. Looking back once over his shoulder he smiled and shook his head. Without saying another word, Junior turned back and waddled towards the exit. 
"Disgusting perverted ghost," he thought to himself. "At least it made Dad's stupid errand worth it."