Disclaimer: Characters belong to Amano Akira. Story belongs to me.
A/N: My own personal headcanon on how Mukuro started truly stepping up to being the other half of Tsuna's Mist. Written as friendship but can be seen as more.
Edit: Made a few spelling mistakes that were pointed out to me so I fixed them haha. *waves hand like a maniac*
Mukuro had questioned Tsuna's faith in him for a long time now. It was a given that the fluffy brunet was naturally forgiving-with certain exceptions(coughIemitsucough)-nevertheless, such faith in someone as far gone as him, well, it was certainly something worth questioning. Perhaps the same could be queried about his trust in the Varia and Byakuran, but Mukuro didn't much care about his reasonings for those people. Tsuna's faith and obvious attempts at getting close to the Illusionist left him feeling puzzled, Mukuro had possessed the boy's friends, had used Chrome to get out of Vindice, practically abandoning her afterwards, still the brunet offered him a place to call home, still Tsuna offered that chance to escape his dark and lonely heart.
Many a time Mukuro had questioned whether the other had any alterior motives, it seemed unlikely but past experiences caused the Illusionist to, nonetheless, be wary of the other. Tsuna might be offering a fake solace only to cruelly shatter any love, faith and trust he had left in his dark recesses. Conceivably, the younger male could also be planning on killing him when he least expected it; yet again an unlikely option, for a person in his position though, it may still be probable. There were, of course, a majority of other conspiracy theories roaming his mind's inner thoughts, they were getting more ridiculous and less likely than the first two however. Mukuro always prided himself in keeping as realistic with these possibilities as he possibly could.
With all these thoughts beginning to deter him from adept concentration, Mukuro decided to confront the other during the brunet's next visit. Coincidentally this confrontation took place as they were seated in the first room they had ever met each other. Mukuro was sitting with his legs apart on the sofa, elbows propped up on his kness and fingers intertwined as they hid his lower face. Tsuna was busy checking that the place had been cleaned properly, making sure that the occupants were remembering to buy food and live in a relatively comfortable atmosphere. It was no wonder everyone had dubbed him 'Mama-Yoshi' behind his back (though Mukuro expected the other was probably aware of this nickname and dimply felt indifferent towards it).
"Tsunayoshi-kun?"
"Hmm?" Tsuna pursed his lips as he scrutinized the few dust bunnies that were beginning to hop around a bookshelf, adding a silent reminder to chastise the other's later for such abvious neglect to their personal wellbeing.
"Why do you trust me so much? What have I ever done to garner that faith from you?" Mukuro lifted his head showing a rare expression of confusion and the slighest curiosity. Whatever response he was expecting it wasn't to be startled by the sigh that left the fifteen-going-on-sixteen year old's lips, as if the reasoning was so painfully obvious that Mukuro was an idiot for not realizing earlier.
Tsuna turned around and walked up to the other until they were but a few feet apart. Staring into the other's eyes intently he scratched the back of his fluffy hair, becuase really he had expected Mukuro to be intelligent enough to realize this much.
"Mukuro, there are many reasons why I trust you. I am strutizingly aware that you don't believe me so I'm going to name a few ok?" Mukuro hesitated, unsure if he should listen, before allowing his curiosity to win over and nodded slowly.
"I'm listening"
"You saved Chrome's life" It was spoken with such a tone that Mukuro realized Tsuna truly believed he cared for her.
"I saved her life to suit my needs" He frowned as he corrected the other's obvious mistake. Tsuna shook his head.
"No. If that were the only reason then you wouldn't have tried to help her after you left Vindice, you entrusted her to me and told-no threatened me to look after her moreover," He continued sharply before Mukuro had a chance to protest at the accusation "You felt pride when she started standing on her own two feet. You love her Mukuro, you're just an idiot for not realizing earlier." Mukuro had nothing to respond with at that bold statement, he simply allowed Tsuna to continue with his-main-reasonings. "Furthermore, you cannot tell me that you allowed yourself to be used as a scapegoat and get caught by Vindice, letting Ken and Chikusa escape, on a mere whim. You care for them like family and, as much as you love to deny it in the hopes that that denial will bear truth one day, you also care for Fran. If you didn't than you wouldn't have allowed yourself to teach him how to use Illusions, nor would you have made him rest up when he overexerted himself during the representative battles and gained himself a fever" Tsuna's voice softened at the end of his statement leaving Mukuro speechless.
"I trust you with my life" He concluded.
"Kufufufu. That does not mean that I trust you" Mukuro conceded. Tsuna smiled.
"I know" Stepping forward he grabbed the Mist's trident watching the other's expression contort into curiosity, he held the trident up, opened his palm and, ignoring the gasp of realization escaping the other male's lips, he cut his open palm with the tips of the trident. Holding out the bleeding hand upside down, letting the blood drip directly within Mukuro's line of vision Tsuna let out one last bit of insight "Should you ever deem it necessary, I am giving you permission to posses my body, even kill me if you wish. This is what you always wanted isn't it?" The smile and tone of the honey-caramel eyed boy before him wasn't challening or condecending, it was warm, understanding and welcoming. Mukuro chuckled before kneeling down on one leg and, taking the offered hand in his own bare one, Mukuro bowed his head.
"You might actually suffer from more insanity than the rest of us Tsunayoshi-kun" He jokingly stated.
"I wouldn't be surprised, what with having all of you plaguing my otherwise boring existence so frequently" Tsuna whispered. Then, "Do you trust me yet?" In response Mukuro turned the hand upwards and lightly pressed his lips against the bleeding wound.
"I trust you" He whispered with clear fondness.
"Mukuro"
"Hm?"
"Never, EVER, do that again" Tsuna squeaked out. Mukuro looked up and doubled over in laughter at the others flushed, embarassed expression.
"Don't worry I will"
"MUKURO!" The brunet yelled in flustered exasperation causing the one who would become the second half of his Mist in the future-though neither knew it just yet-to laugh even louder. This was the scene that awaited Ken, Chikusa and Chrome as they entered the main room, much to their clear as day bafflement. In the end Tsuna and Mukuro kept the events that transpired that day to themselves and never openly spoke of it again, in fact if it weren't for Mukuro sometimes using his Mist flames to lightly caress that scar or, even, the times he would kneel down and kiss it himself when on his own with the honey-caramel eyed male, Tsuna might've forgotten about it. Well, at least he had gone from being embarrased at such a display to mildly annoyed before settling on indifference, after all everyone had their own quirky ways of showing their gratitude to him-even if he preffered they didn't.