Unlike in European languages, Japanese has a plethora of “I“, and it is extremely important to use a right one depending on the occasion.
While you can see all choices through the above link, the standard ones are as follows:
- Formal occasions and formal writing: “私(わたし or わたくし)” for both men and women. “わたくし” is more formal than “わたし”
- Casual occasions: “僕(ぼく)” for men, and “私(わたし)” for women
- Men (in adolescence and after) between friends also commonly use “俺(おれ)”