1) Please tell me can we pray in a house or room where Japanese worship Buddha?2) We are three Muslims in Japan for three months, can we pray the prayer of Friday?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

According to the view of the majority of Muslim scholars, performing the prayer in non-Muslim places of worship is valid although it is strongly detestable. Muslim scholars believe that such places are shelters for devils; praying wherein devils assemble is undesirable. Such a ruling is based on the Prophetic Hadeeth in which Abu Hurayrah said: "(One night) We slept with the Prophet () and we did not wake up until sunrise; i.e., they failed to perform the Fajr prayer at its due time and they performed it after sunrise." Thus, the Prophet said: “Every man has to seize his mount by the head and move suddenly and rapidly, because the devil is present at this place.” [Muslim]

The Prophet ordered his companions to perform the prayer at another place because the devil was present wherein they slept. In addition, such places are full of images which prevent the presence of angels. In this vein, the Prophet said: “Angels do not enter a house wherein a dog or picture is present.”

Some scholars of Islam believe that it is forbidden to perform the prayer in such places. Thereupon, to avoid such a disagreement between the two parties, it is better to abstain from praying in such places.

Also, praying in such places may contribute to show that non-Muslims constitute the great masses. This ruling applies also to those who enter such places without need or direness. Anyway, it is not detestable for one who is compelled to pray in such places.

As for your second question, please refer to Fatwa 83782.

Allah knows best.