>>686298It depends on how serious you are, most people tend to give up easily.
You can learn both kana (Hiragana / Katakana) in just a few days. there's a game called My Japanese Coach that you can play on a DS/emulator, it can teach you the very basics and is really comfy and fun.
for Kanji there's an app often recommended as the best one called Kanji Study and if you use mnemonics with it then you can learn faster, for example drawing something besides the kanji character that you can memorize. Some kanji's are pictorial like 山-mountain 川-river 目-eye etc. if you put some effort you can apply that process to the others as well. once you're more comfortable you can try Anki's cards and visual novels for vocabulary, sentences etc.
