Firstly, the Japanese Constitution prohibits the deployment of the JSDF outside of Japan and is also the reason why it's called a "Self-Defence Force" and not a military.
Secondly, it already is fairly large and is really well equipped. Despite the name, it is quite capable. Abe has been increasing military budgets for a while now and it shows with the JSDF.
Thirdly, everyone should remember that Japan is far more than just Shinjuku cosplayers or Akihabara nerds. All the weird stuff is exaggerated and amplified - Japan isn't actually crowded with tentacle porn, nor are there vending machines selling used panties on each street corner. While the hikikomori problem does exist, it is a fringe thing. Japanese youth at large are no more inept when it comes to social interactions than their Western counterparts. You morons watch too much ****ty anime.
Fourthly, Japan has not done the same cultural soul-searching that Germany did after WW2. There still exists a strong Nationalistic element in Japanese politics. This is why South-Korea and China and Taiwan and even Philippines are quite vary of the resurgence of militarism and nationalism in Japan. However, the threat should not be exaggerated, as there is a quite strong leftist and pacifist element too, that acts as a counter-balance.