^nah, 1-2 months is fine to reach talking intermediate level @7-8+ hrs a week practice. but learning to read write it is a time consuming job, i agree. it will take years.
for translating a manga, using nowadays modern tools like an android tab + pen with google translate it will be cakewalk after reaching talking intermediate level.
if u're familiar with grammar of indian laguages & english, grammars from most other language is simply no big deal.
I was talking about the complete language, not just modern spoken Japanese. To be proficient you need to practice your writing.
For manga, being able to speak is less of a concern than being able to read. Google translate is bad at translating Japanese to English.
I know that the grammar is not a big deal. It is the Kana and Kanji that is.