[Jawful]

This also applies to ぶ and ぬ verbs

む-verbs：読む(よむ)→読んだ(よんだ) read → read (past)
ぶ-verbs：遊ぶ(あそぶ)→遊んだ(あそんだ) play → played
ぬ-verbs：死ぬ(しぬ)→死んだ(しんだ) die → died

Keep in mind the kanji isn't what's important. The ending is. Look into て-forms of vebs. It's directly related. All of these words also go to で for the て-form. （読んで、遊んで、死んで）If you haven't studied て-form yet, it'll all make sense once you have. Good luck with your study.