Read a lot of both light novels in the original language and in the 'ca' language. This helps in getting familiar with the different styles and common expressions. For example, if you read many Japanese light novels and their Catalan translations (assuming 'ca' is Catalan), you will start to notice patterns in how certain things are translated.
Study the cultural backgrounds of both the source and the target languages. Since light novels are full of cultural elements, understanding the cultural context will make the translation more accurate. You can take courses or read books about Japanese culture if translating from Japanese to 'ca', and also study the culture where 'ca' is spoken. For instance, if 'ca' is Catalan, study Catalan culture and history.