なぜなら
何故なら
nazenara

Conjunction

1. because; the reason is; if you want to know why

Usually Written in Kana
いておどろくなよ!今日きょうからおれはピアノをはじめるんだ。なぜならわたくし音楽おんがく先生せんせいになりたいからだ!
kiite odorokunayo! kyōkara orewa pianō hajimeru nda. nazenara watashiwa ongakuno sensēni naritaikarada
Brace yourselves! From today I'm learning the piano. Why? Because I want to become a music teacher!