Welcome, Lucius. Learn japanese is not tough at all. Based on my experience, if you want to read without help of any tool (e.g. JParser to put furigana above kanjis), one~two years might be insufficient time to learn enough kanji and vocabulary. Well, it is because I did wasted time instead study kanji hard, so I think I took more time. Anyway, I do not want to desmotivate you, I think if you study kanji hard (unlike me), maybe you can do it in 2 years. If you do not care about kanji (you can even put furigana above the kanjis using tools), you should be able to read easily the majority of visual novel in 1-2 years.