I've posted this before, but learning Hiragana and Katakana is one of the highest return investments in terms of passive Japanese learning, because it lets you pick up and check words as you hear or see them. Katakana is for Engurishu loan words and will help you read tags, while Hiragana is for actual Japanese words.
Go here to learn Kana today:
https://realkana.com/Also, bookmark this, it's useful not only for checking words but also for Kana-to-romanji conversion when you want to double check your reading or are just lazy:
https://translate.google.com/?sl=ja&tl=en&op=translate 