I'm Arum Choi, a librarian of DGIST Library. 

You have many options to search for patent information, 
and I recommend these two options for your Japanese patent search.

1. WIPS ON(Patent DB, DGIST Library Subscription)

 1) Access to ‘WIPS ON’ database(click)
 2) Click the Registration menu (회원가입)
 3) Make on your user ID & User verification by your DGIST e-mail address
 4) Fill out your Verification Code & User Info. 
  • Verification code will be sent to your DGIST email.
  • After typing the code user verification process will be finished
 5) Sign In to database https://www.wipson.com
※ How to Use WIPS On: https://www.wipson.com/service/cts/userGuideManual.wips

DGIST members can access all subscribed e-Rsources (includes WIPS ON) from anywhere in the following ways.
 1) Log in to Library Website (https://library.dgist.ac.kr/) > E-Resources> Academic Databases > W > WIPS ON
 2) http://libproxy.dgist.ac.kr/_Lib_Proxy_Url/https://www.wipson.com/ > Log in for off-campus access (Portal ID/PW) 
※ Off-Campus Access: https://libguides.dgist.ac.kr/Off-Campus

2. J-PlatPat(Japan Platform for Patent Information, for free)

 - URL: https://www.j-platpat.inpit.go.jp/
 - How to Use J-PlatPat: https://www.j-platpat.inpit.go.jp/manual/en/topics/info.html

If you have any questions about using e-Resources please contact me.
Best regards, 
Arum Choi