The Gakken SX-150 Mark II

SX-150 markII Analog Synthesizaer 学研大人の科学アナログシンセ第二弾！

YouTube Published on Oct 30, 2011 by jetdaisuke
You might remember the original came with a Japanese magazine as a kit which had a cardboard back. This one appears to be all plastic. See the Gakken label below for more.

"It has been back! 赤くなってアイツが帰ってきた！学研 大人の科学マガジン付録として大ヒットしたあのアナログシンセが、単体製品として復活・アップデート。見た目はおなじでもシンセサイザーとしては劇的に良くなってるぞ！
ブログ記事：大人の科学シンセに新型 SX-150 Mark2が登場したぞ
http://gajetdaisuke.com/archives/111030_150531.php
学研さんよりレビュー用に一台ご提供いただきました。"

Googlish: "Turned red guy is back! Analog synths that hit Gakken Adult Science magazine as a supplement, update revived as stand-alone product. In the same look as the synthesizer I'll become dramatically better!
Blog: SX-each new adult science synth appeared 150 Mark2
http://gajetdaisuke.com/archives/111030_150531.php
Submitted for review by a single offer from Mr. Gakken."

You can find the mark II on Amazon Japan.
You can still find the original on eBay and Amazon.