All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Circumcision is one of the acts of Fitrah (matters that correspond to the nature of man) and the Lawmaker has emphasized it. Imaams Muslim, Al-Bukhari and others narrated that the Prophet, sallallaahu ‘alayhi wa sallam , said: “Five things are parts of one's Fitrah: shaving the pubic hair, circumcision, trimming the moustache, removing the hair under the armpits and trimming the nails.”
The scholars have three well-known different opinions on this:
1 -It is a Sunnah (i.e., recommended) for men and likable for women.
2 -It is obligatory for both men and women, and this is the view of the Shafi'i school of Fiqh (Islamic law).
3 -It is obligatory for men and likable for women.
The scholars, then, have different opinions on this matter because there is no explicit sound text (Quran or Hadeeth) upon which the rule could be based. It is only that each group of scholars has a given opinion with some evidence that the other group rejects for not being sound or failing to be indicative of where the disagreement is. They give instead their own opinion. In any case, circumcision is more established and stressed for men than it is for women as it is difficult for the non-circumcised man to be fully certain of not having some dirt or urine on his penis, and this is not the case for women. As for our Japanese brothers, you should make clear to them that circumcision is one of the Fitrah's basics which are part of the religion and which are from Islamic rites. It is also a feature of Muslims as opposed to non-Muslims. Muslims are known to be circumcised. Circumcision has many purification-related profits. Tell them also that Ibraaheem the father of the Prophets, got circumcised at the age of eighty as narrated by Al-Bukhari and Muslim . Try also to clarify to them that what they fear is no longer a problem as there are now very modern surgery techniques. This is for men. As for women who have passed the age of adolescence it is better not to ask them to do circumcision as there is no text asking them to do so and when there is no order to do something or to leave it, the person then has the choice.
Allaah Knows best.