I made a interesting perspective based on another fic I read
My oc Fujimori Kiyomaru, Tsuna's only childhood friend, Lightning Flames
Reborn manipulated him into fighting the Varia to save Lambo and 'protect Tsuna', he is pretty much the only one that doesn’t like Reborn
As the Lightning Guardian, a blood powerful one, the Vongola demanded him to be the meat shield for their last surviving heir, and made sure he knew that. Tsuna protested, but didn't do much because Reborn shoot him and told him to shut up
With time, watching Tsuna befriend those people that ignored his wishes and only cared for his status as heir, while doing nothing to help the only real friend he had, their friendship soured
Kiyo grew tired of begin in this fake family, of Tsuna just letting Vongola use his friends, he remembered when CEDEF come after Fuuta for information and rankings, when they came to use his friends as disposable and Tsuna did nothing
Watching Tsuna smilling and laughing with Nono - his 'grandfather' - and his Guardians, Reborn - the hitman who BLACKMAILED and THREATENED him into fighting a assassin squad and putting his loved ones in danger - begin treated as a dear chaotic mentor and him - stuck as a Meat Shield because his life has even less value than Tsuna...
For all he TRIED to protect Tsuna from Vongola...
Those people ruined Tsuna's life and he is not even angry at them? He is stuck in a gilded cage and seens confortable in his delusions? Don’t even care for all manipulation and threats they did to both of them?
So much like Sawada Nana
So he left, angry at his former friend for begin so spineless and cowardly boss that cant even stand up for his friends, not before throwing the Lightning Ring on Tsuna's sad and stunned face and calling him a awful friend, and getting in a fight with Gokudera for 'insulting the Tenth' and begin called a coward for running away.
He might join Millefiore maybe?
