This is the basic grammar AはBだ meaning “A is B”.
The A: 決めるの
決める is a verb dictionary form meaning “to decide”. The particle の is what is called the “nominaliser” which makes a verb or adjective before work as a noun. So 決めるの means “the one who decides”.
The B: 我
It means “I” or “me” which is hardly used in real life as the first person pronoun. It is very old and archaic so in anime it’s often used by high ranking samurai or kings. So if you call yourself 我 in a real conversation, you might sound very arrogant, or it just sounds funny.
我 is actually used in real life as the second-person pronoun “you” when insulting someone, especially in the Kansai region. It is very rude and offensive so you’d better avoid using it. In this usage, it’s often written in hiragana or katanaka.
ware, nani shiton nen!
What the f**k are you doing?!
* しとんねん (Kansai dialect) = してるの
In Japan, there are many ways to say “I” or “me” depending on gender, age, situations, regions, and so on. So I will introduce some of the first person pronouns commonly used in real life.
The most common first person pronoun is 私. For females, It can be used in both casual and formal situations, so if you are a woman, you can just stick to this. If you are a man, 私 is usually used in formal situations such as job interviews, formal speech, or whenever you talk to clients or superiors. In casual speech, men tend to use 俺 or 僕. So what’s the difference between them?
俺 sounds masculine and informal, whereas 僕 sounds softer and more formal than 俺. 俺 is often used when they talk to their family or close friends as they want to be cool and manlike rather than being “a good boy“. 僕 can also be used in semi-formal speech but when you’re not sure which pronoun to use in a formal situation, just use 私 as it never sounds rude.
It means “The one who gets to decide is me” or “It is me who gets to decide”. As you know, in Japanese a noun usually comes first and a verb comes on the end of the sentence, but by using this grammar “verb or adjective plain form + のは + noun + だ”, you can emphasise the noun.
More First Person Pronouns
- わたくし: more polite than わたし, used in very formal situations.
- あたし: more informal than わたし, used by females in casual speech.
- うち: used by girls in casual speech in western Japan.
- わし: used by men in casual speech especially in the Chūgoku region. In anime, it is often used by old people but you rarely hear old people using わし in the Kanto region.