When you think of plastic models, you probably think about cutting out parts from those leftover frames (called "sprues"). Painting said parts. Then, putting the kit together to make a robot, a car or an aeroplane. You probably do not think of sex toys.
As Kotaku Japan points out, this plastic model kit isn't your typical model. It's a build-your-own-vibrator kit and comes in a retro style box that proudly points out that the model is so easy to build, anyone can do it. (It also says that you can even customise your vibe, but the retailer does warn about how you customise it!)
The product's concept and packaging are novel and totally tongue-in-cheek. This looks like something you'd see for a Japanese robot toy from the 1960s or 1970s -- not a sex toy.
This type of vibrator is called a "rotor" (ローター) in Japanese. In English, it's a "love egg". Put together your own for a mere ¥630 ($6.55). It's available at the Japanese sex toy retailer in the link below.