To this day I think that khr did gave us one of the easiest yet most entertaining sorting systems in animanga. I can spend hours and hours and hours sorting characters on the sky element/attributes system. Easy logic, concise explanation, made for found families and friend groups, all the fun and none of the nuance.
For the ones who doesn't know, it goes like this:
SOME STORY CONTEXT (not really important):
Katekyo Hitman Reborn! is a manga about an Italian mafia family that is in need of a successor, but everyone has been killed except Tsunayoshi Sawada, a japanese kid that is The Loser™. The Vongola, said mafia family, send a hitman that happens to be in a baby form to train him and protect him: Reborn. He trains Tsuna by shooting him on the head with a Vongola special bullet, the Dying Will Bullet; if the person shot has regrets, they will reawaken (only the underwear survives at first) with a flame on their head, the Dying Will Flame. As long as the flame last, the person is on Dying Will Mode and their abilities are enhanced, almost like a super or something, by turning all the internal safety switches off.
THE BASIC TERMS FOR YOU TO KNOW:
What we care about is the Dying Will Flame. It is a form of high-density energy refined from one's own life force. The Dying Will Flame has similar properties to a real flame and it has levels of purity (the greater the resolve of a person, the clearer and most powerful a flame will be), attributes (different flame elements; you can be born with multiple attributes, but it can't be learn without a previous affinity), and types (in the manga there are the Seven Flames of Sky and the Seven Flames of Earth; we'll be talking about the Seven Flames of Sky only, as to not give major spoilers).
In the KHR! World, the users can channel their Dying Will Flames through tradional weapons to attack or they can use them to open up certain special devices with different purposes (including functions as containing more weapons or food or daily life objects). However, the most notorious use is for the mafia bosses and their guardians, their inner circle of subordinates. Using seven rings specially made to channel the Dying Will Flame, they can fight or use them on their pure form to attack, defend and even heal others.
NOW, THE REAL FUN. THE SORTING.
As the name says it, the Sky Flames are divided in seven attributes (also called elements). Those are named after phenomenons that happen on the sky: Storm, Rain, Mist, Lightning, Sun, Cloud and Sky itself.
Traditionally, the Sky was viewed as a leader attribute and their users' mission was mainly to understand, accept and influence their subordinates. Something like the sky, that encompasses all the other phenomenons and allows them to be as their are. However, for the sake of having fun, you could give the "leader" of your group another attribute and play with the role of the sky flame!
THE SEVEN FLAMES OF SKY !
SKY FLAME: as said before, it's the common attribute for the leaders. That's because A) the Sky Flame can achieve the greatest level of purity and B) it can open any special device. It symbolizes the extensive and all encompassing influence of the Sky over the other elements. It's personal attribute is HARMONY and it's role is to balance things out. The Sky Flame color is orange.
STORM FLAME: an attribute common for the relentless, the Storm Flame user should be the unstoppable base of attacks of the family / group. It symbolizes the storm that fiercely spins with no end and for that its attribute is not other than DISINTEGRATION. The Storm Flame can only open special devices made for itself and its color is red.
RAIN FLAME: the role of the Rain Flame user is to prepare the family / group for the fight, cleaning the blood spilled and bringing the calmness factor. It can also only open the special devices made for the same element, but as it is to be expected, its attribute is TRANQUILITY. The Rain Flame is blue and it symbolizes the flood that cleans it all.
CLOUD FLAME: the untouchable users of the Cloud Flame are known for acting as a distant floating cloud that cannot be contained and follows its own path. Its another element that can only open special devices made for itself, but the Cloud Flame color has more a purple tone and its attribute is PROPAGATION. Their role is to protect the family from the outside and never get caught.
MIST FLAME: with a lilac tone, the Mist Flame belongs to those who pretend something exist or not to confuse the enemies and protect the real form of the family / group. As all the other elements, this Dying Will Flame can only open special devices that match its signature type. Its attribute is CONSTRUCTION and, as you cna imagine, it symbolizes the untouchable fraudulent illusion.
LIGHTNING FLAME: more than anything, the Lightning Flames is known for striking with remarkable force. Its attribute is HARDENING and, its color is green and as all the rest except for the Sky Flame, it cannot open special devices that doesn't match its attribute. The role of these users is to absorb the damage to the family / groups like a lightning rod.
SUN FLAME: At last, the Sun Flame has a yellow color and its attribute is known as ACTIVATION. Those users of the Sun Flame must destroy whatever is unfortunate for their families / groups with their own bodies and shine like the sun over all the rest. It is the sixth flame that cannot open any special device not mafe for itself and it symbolizes the sun that brightens up the sky.
TO SORT YOUR CHARACTERS all you have to do is think about what description they match better. You can follow the khr canon and sort characters by groups of seven first, one for each attribute, and if you have more then you can sort them as special characters. Or you can match it the way you better like it, disregarding order and putting (for example) three rain flame users in one family with not sun flame user in sight.
Feel free to link this plot in your owns or reblog it to explain to your users how the Dying Will Flame thing works! And don't forget: this sorting it's for you to enjoy.