One of the challenges for people studying Japanese is the use of first-person pronouns. Japanese has a wide variety of first-person pronouns, and their usage can be complex. Let's summarize the key points while looking at how many types there are and what you need to know to be okay with them.
[Main first-person pronouns commonly used in present-day Japanese (corresponding to "I" in English)]
In Japanese:
Watashikushi (written in kanji as 私) - Used when speaking in the most polite manner. It is gender-neutral.
Watashi (written in kanji as 私) - A more casual form of "watashikushi" used in everyday language. The "ku" in "watashikushi" is omitted. It is gender-neutral.
Atashi (written in kanji as 私) - A casual expression of "watashi." Mainly used by women in spoken language. The "wa" in "watashi" changes to "a."
Atakushi (written in kanji as 私) - A casual expression of "watashikushi." More polite than "atashi." Mainly used by women. The "wa" in "watashikushi" changes to "a."
Ore (written in kanji as 俺) - A first-person pronoun commonly used by men to refer to themselves. It is generally used both informally and formally, starting from the age when children become conscious of being more mature and continuing into adulthood.
Boku (written in kanji as 僕) - Similar to "ore," it is commonly used by men as a first-person pronoun. It is used formally regardless of age and gives a softer impression compared to "ore."
Jibun (written in kanji as 自分) - A first-person pronoun used to refer to oneself. Commonly used by sports-oriented men.
Washi (written in kanji as 儂) - An abbreviation of "watashikushi" or "watashi." It is often used by older men, but nowadays, fewer people use it.
In addition, women and young children often refer to themselves using their own names. The use of first-person pronouns in Japanese is influenced by factors such as history, gender, age, and situation, defining various elements such as personal impression, social status, and the sense of distance with others. If we include older forms of expression, there are many more first-person pronouns beyond those mentioned here, with around 60 other possibilities. In modern times, understanding from 1 to 8 above should be sufficient. Among these, Japanese individuals have the freedom to choose and generally use 2 or 3 different ones depending on the situation.
I would be glad if you could refer to this information when watching anime, manga, dramas, and other media.