Granblue fantasy

There's no need to overthink things and just translate as is. The same applies to cultural nuances and differences; there's nothing stopping us from using "-chan," "-kun," etc., in the English text. Even someone completely unfamiliar with these things wouldn't need significant intellectual effort to understand the general meaning after a two-minute Google search. But it's like with dyslexic fans of dubbing who "want to observe what's happening rather than read subtitles."

If the work clearly emphasizes the Japanese cultural context, using "-chan" and "-kun" is logical. If, however, they are a feature of the language of the work, but the work itself develops in a different cultural space (neutral or, even more so, distinctly non-Japanese), and the author confirms that it can be translated, then why not translate it. For example, "sensei" in a British school is clearly "mister" or "teacher," etc. Dubbing fans are completely irrelevant here. The absence of translation guaranteed does not interfere with the work itself, but a poor translation can easily do so, in both cases (either by not translating everything that could be translated for the most accurate transmission of the idea, or by translating what shouldn't be translated, as the idea is better perceived in its original form, even if it requires using loanwords or something else).