When you either at the age of the year, you started learning their first language, their text which they taught you to kill outside the book and to compose verbs? You heard and learned from the observation that you are learning Japanese in Singapore again. Immerse yourself in as many languages as possible, giving you the best chance to absorb it and the child feels like learning your mother tongue.
With that you can understand that the best way to learn is Japanese and you will have a language 24/7, but probably. It is the best and fastest way of learning, to go to another country, though there are other ways in which you are immersed yourself without going STW.