You're going to have a very hard time doing the lessons if you haven't learnt both types of kana yet. Katakana is important too, not just hiragana.
The "onyomi" in the kanji lesson are listed in katakana. So you will not be able to read half the readings, but will only be able to read the "kunyomi" ones, unless you learn katakana.
In reality, both kunyomi and onyomi are written in hiragana. The only reason onyomi have been written on the lesson page in katakana is to separate them more clearly from kunyomi.
So, いち, に, さん, し, ご, ろく, しち, はち, きゅう, じゅう are onyomi type readings. But they're written only on the lesson page (and most Japanese dictionaries) in katakana, like: イチ, ニ, サン, シ, ゴ, ロク, シチ, ハチ, キュウ, ジュウ.
Again, this is just dictionaries. When actually writing them without their kanji, you writeいち, に, さん, ...
May 3, 2015 at 11:17am