What is the Reason for increase of the Bitcoin?
Steady increase in demand and limited fixed supply of 21 million coins.
Japan accepting bitcoin as legal payment.
People all over the world getting aware of bitcoin's potential.
New companies starting to accept bitcoin as payment.
I think also that this are the reason why bitcoins price is still increasing. People are now getting aware about bitcoin and they use it on their daily transaction that causing of increasing of demand. Yet, Japan are now accepting bitcoin so that new companies are accept bitcoin as payment.