The difficulty of learning a second language depends on your fluency in other languages. For Korean speakers, Japanese will be easier to grasp because sentence structures and vocabulary pronunication is similar. For English speakers, however, Japanese is more challenging because it is one of the most removed languages in grammar and vocabulary. In addition, the writing system is completely different. But, if you try think about it as just taking more time to learn rather than being difficult, you may find more satisifaction in your study progress. There are, however, parts of Japanese that are simpler than English. For example, Japanese nouns have no plural forms or genders. There are only two tenses: non-past and past. There are only two irregular verbs in the entire language. Japanese is easy to pronounce with its five pure vowels that have consistent pronunciation. The short answer for native English speakers is that Japanese is difficult, but there are parts that you may find much easier to learn that other European languages. In the end, your success will depend on your goals, motivation and mindset.