how to climb up to Kikuseidai observation

I believe the only way of EASILY going up Mt Maya for the Kikuseidai observation is by the ropeway.

Address: Hyogo, Kobe City, Nada Ward, Mayayama-cho 2-2
Ropeway times: 10:00-17:30 on weekdays, 10:00-20:50 on weekends and holidays
*Detailed timetable information available on the website
Closed: Tuesdays (if a public holiday falls on a Tuesday, the ropeway will close the following day instead)
Wi-Fi: Yes, at Star Station
Price: 1570 yen for adults (round trip)
Phone: 078-861-2998 (Star Station)
Homepage: Mt. Rokko and Mt. Maya Aerial Ride

Other ways you can go is by hiking up.
you can hike up from Maya station. Although the maps are in Japanese it is still quite easy to navigate. It will take around 2~, 2.5hrs
It offers nice paths through the wood, once a while a fantastic view an some shrines and old temple ruins on the way.
The night view is astonishing, one can see the whole Osaka Bay. There are much more paths to walk than strait up, it might be worth exploring them.

you can also go by car and You can try park the car up to the gate where they stop people from driving, instead of the carpark which costs 500 yen and further away, since police rarely comes there, according to locals.