何故なら
1
conjunction
porque
1
conjunction
because;the reason is;if you want to know why
聞いて驚くなよ！今日から俺はピアノを始めるんだ。なぜなら私は音楽の先生になりたいからだ！
Brace yourselves! From today I'm learning the piano. Why? Because I want to become a music teacher!