What is the existence of God?

In Buddhism, gods are creatures of a higher level than humans, such as heaven and bonten.
If you think about reincarnation as a premise, there is a possibility that humans will also be reborn into heaven (God).
Also, there is a possibility that God will die and be reborn as a human or animal.
Incidentally, a Buddha is someone who has awakened to the truth, such as the Buddha.
The Buddha is superior to Heaven and Bonten (or rather a different level).
The Buddha has been freed (graduated) from reincarnation.

So, if the gods of Japan were simply included in the Buddhist worldview, they might fall under heaven or bonten. Or they may worship people who had particularly strong powers among humans as “gods.” Sugawara Michizane → Tenjin, the god of learning, etc.
However, when Buddhism came into Japan, it transformed into Japanese thought, and a way of thinking called the Honchisui Jakusetsu (Honchisui jakusetsu) was born.
The local area is the true identity and main body, and a trail is something that comes out in disguise.
The native place is a Buddha, and the Buddha appeared by transforming into the form of a god in order to guide people, so they believed by attaching an ancient Japanese god and a Buddhist Buddha together.
It seems that gods, etc. called ○○ gongen (Gongen) fall under that category.

I don't know what the god of the house is, but it may be a type of creature called “heaven” that has lived in Japan for a long time.
As a characteristic of Japanese gods, it is said that they hate injuries such as death and blood.
(There is a possibility that the injury mentality was useful in preventing infectious diseases in terms of hygiene. (The same goes for cleaning with salt.)
Therefore, when someone dies at home, there is a custom of covering the kamidana with paper to hide it.
Also, there were cases where women with blood due to menstruation were unable to pray at the shrine.
The fact that women don't climb the sumo ring may also have something to do with that.
There is no idea of injury in Buddhism, so monks were able to mourn the dead without worry.

　Basically, the gods for Japanese people are 8 million gods. Each one of nature, such as mountains, rivers, seas, rocks, springs, earth, fire, wind, thunder, trees, grass, etc., is thought to be God's devotion (place where gods descend), and furthermore, they have been thought to be gods themselves. Also, Toshigami comes down to the village at the beginning of the year, spring comes, sprouts appear, brings harvest in the fall, and they return to their place from the village. There is an ethnic history where the cycle of one year and four seasons has been accepted as the traffic of the gods of the year.

The kamidana of the house is a place where such gods are enshrined. Basically, it is a place where the god of that land (god of soil production) is enshrined. Since Shinto centered around Ise Shinto, the main shrine office has taught that “Amaterasu Omikami is enshrined in the center of the kamidana, local guardians are enshrined on the left, and revered gods are enshrined on the left.”
As I wrote in the title, Buddhism and Shinto have been established and developed in a form where they coexist in Japan. Some denominations insisted on the position of “not worshipping sacred instruments,” and there were cases where they denied enshrining kamidana, but most Buddhist religious groups have coexisted with Shinto.

Even at Buddhist temples, gods have been enshrined as guardians to protect temples. Buddhism has taken a tolerant attitude towards existing religions when proselytizing since the time of Buddha in India, and has adopted existing religions without denying them. Even if it is an ancient Indian god, it is positioned as the “guardian deity of Buddhism” in sutras, etc., and when a Buddha statue is enshrined as the principal image in a temple, Indian gods are now enshrined as the Four Tenno, 12 Jinsho, Five Daimyoou, Daikokuten, Kisshoten, Taishakuten, and Benzaiten in temple grounds and halls. This trend was transmitted along with China, Korea, and Japan when Buddhism spread. The Seven Lucky Gods, Fukurokuju and Hotei are gods of Chinese origin.
Most temples in Japan enshrine some kind of god as guardians to protect the temple. In the process of considering and becoming established, the local shrine theory that “Indian Buddha and Bodhisattvas changed their appearance and became Japanese gods,” Hakusan Gongen's native place was regarded as the eleven-faced Kannon, and the local area of Atago Gongen was used as Jizo.

Furthermore, in monotheistic religions such as Christianity and Islam, God is an absolute god and creator. It can be said that this god originated from a climate and culture quite different from Shinto and Buddhism.

You can ask God for benefits in this world, such as praying for traffic safety, prosperous business, and safe delivery, and ask Amida Buddha to take you to the Pure Land of Paradise when your life runs out.
Let's respect them both.
Namu Amida Buddha