Okay, so I'm still working out a lot of the lore, but I'll just post what I got for now and add more later.

Eranda Bassho 

Other names: Eranda

The world I created for my story. Basically a mashup of different cultures and times.

Seiken

Other names: none

Created by Taiyo Nagare, or rather the God Ten No Hono and ruled over by multiple gods Seiken is a world no one knows exists. It is the home of the setsuzoku's and its in trouble

Hozei-Zumi:

Other names: HZ's, HoZu's

Hozei-Zumi are humans born with special powers and birthmarks on their bodies. Both of these can vary in shape and type, but the marks are usually some sort of animal or mythical creature. No one knows how or why this happens or even what the marks are for other than showing that the person is different. 

You can tell a person is a HZ as soon as they are born due to the birthmark they have, as they grow, their traits will begin to show even more, ears, tails, horns claws and fangs, even patches of fur or scales corresponding to the creature depicted in their mark. These changes are not only linked to the age of the hozei-zumi but also their power level.

At age 18 all HZs gain a large boost in power, this allows them to be able find their mate, it is also the main time you start to see the fur or scales appearing on their arms or legs.

Being a HZ is not hereditary, it is completely random, having HZ parents does not increase the chances of the child being a HZ, nor does having one or two human parents decrease it.

Hozei-Zumi, depending on their age and power level, can change form, they have three different forms.

The first form is the one they are born into, mostly human with their animal traits.

The second has more of the animal characteristics, more fur or scales, hands may become more paw like, feet will become paws or hooves, someone with a water based setsuzoku may become a merperson, etc.

The third and final form requires the most power, this is when the HZ can take on the same form as their setsuzoku.

 

Setsuzoku:

Other names: Setsu's

A Setsuzoku is a creature that appears the moment a Hozei-Zumi is born and matches the birthmark they have. They can can be any kind of creature, mythical or otherwise. 

A setsuzoku will stay with their HZ all their life, growing with them and teaching them about their abilities. They are capable of speech and can change their size at will. 

The connection between Setsuzoku and Hozei-Zumi is where their powers - and animal traits of course - come from, the closer the connection, the greater the power level.

If a setsu is killed, their HZ companion will lose their powers but not their traits since they are a part of their bodies.

Setsuzoku are only visible to Hozei-Zumi. Because of this, regular humans are unaware that the Setsuzoku even exist. 

 

Saisho:

Other names: The Festival of the First

THe day the first Hozei-Zumi was born.

A time when the link between the worlds of Eranda Basho and Saiken is the strongest. On this day, every HZ gathers together at a chosen place to celebrate and - any over the age of 18 - to find their mate.