Kōga-ryū

The Koga Guild, much like their Iga counterparts and normal shinobi divide their teachings into many parts. Ninjutsu, Genjutsu, Taijutsu, and so on. The reason why they did this is quite different from normal shinobi. They didn't do this because they learned how many ways chakra can be used back when chakra first appeared, but did this to learn how to use chakra for certain situations. This allowed them to focus like normal shinobi, but it also made it a lot easier to use the different types of jutsu together for a lethal combination. In short, Kōga-ryū is a fighting style revolving around learning how to use all jutsu types in unison to create one large and expansive fighting style whose capabilities extend past what normal shinobi can do because of the unity.

Description
The Kōga-ryū hind Kōga-ryū is very similar to the principle behind the Elemental Progression Techniques. It is the progression of one jutsu type to another within a single technique. This shouldn't be confused for stuff like Nintaijutsu for that merges two jutsu types. Instead, it can be described as using one jutsu type to "evolve" the capabilities of the techniques original jutsu type. For example, if one were to use the Genjutsu Demonic Illusion: Descending Hell Technique and happened to have Fire Release they could use the functions of Ninjutsu to "evolve" the Genjutsu technique so that there really is tremendous ball of fire falling from the sky or vice versa and use the basis of Genjutsu to make a Ninjutsu technique like Fire Release: Great Fireball Technique transform into a Genjutsu to seemingly have the power over reality itself. This is just one of the many ways shinobi who use this fighting style progress a jutsu type to another. Unlike the examples provided above, the act of progressing a technique's jutsu type can often result in abilities that neither jutsu type can do on its own. One example of this is using Genjutsu's ability to tap into the minds of others to "evolve" Ninjutsu so that their techniques slowly change and adapt to the opponent's fighting style, skills, and mindset.

The most common way the fighting style is with Taijusu, Bukijutsu, and Chakra Flow. Progressing these jutsu types allow them to use weaponry with hand-to-hand combat so effectively that it looks like "their bodies are transforming into weapons and back into limbs." Considering what Kōga-ryū is this may actually be an ability that is well within their grasp.

Unique Jutsu Types
In addition to the common jutsu types, Kōga-ryū has a additional jutsu types that are unique to the fighting style and it alone. The unique jutsu types usually follow with the idea behind Kōga-ryū and are usually the result of "evolving" one jutsu type with another in a very specific way instead of any old way like with the Kōga-ryū outside of these jutsu types.

Shinobi-iri
Shinobi-iri is the result of using the premise of Genjutsu to "evolve" the premise around using Ninjutsu oneself. This allows the techniques derived from Shinobi-iri to revolve around masking one's presence in various ways by making ones presence illusory. This makes Shinobi-iri comparable to Izanagi because it to is about turning oneself into an illusion to seemingly fade in and out of reality. Unlike Izanagi, the techniques revolve around stealth and not dodging fatal blows.

Shinobi-iri also refers to skills involving infiltration that has to deal with chakra in some way. The usage of chakra augments their infiltration abilities to near flawlessness.

Kukushi Bukijutsu
Kukushi Bukijutsu is a jutsu type that uses the idea behind illusion part of Genjutsu to "evolve" Bukijutsu to gain the ability to craft and use weapons that on the border between illusion and reality. The illusive nature makes the weapons impossible to detect with the physical senses, but the illusion is so real that it can still hurt opponents so it seems like users are attacking with "nothingness." It appears like Dōjutsu users have a fairly easy time seeing the weapons and the same can be same with sensor, except it is a bit harder for them.

Gokui Atemi Sakkatsuho Zukai
Gokui Atemi Sakkatsuho Zukai are the secret finishing techniques of the Koga Guild and they are often used on assassination missions.

Triva

 * Kukushi Bukijutsu and Shinobi-Iri was inspired by Stealth from Fairy Tail.