According to a Toshiba program list in MSX Magazine (1984-06), HX-S315, HX-S316 and HX-S317 are programs from the にこにこぷんシリーズ by NHK (search for にこにこぷん here on GenMSX to see the programs)
However it does not seem to specify which programs from the series are sold by Toshiba (there are more than 3, and which is which...)
The full text says:
HX-S315~317
2800 Yen
16k RAM
NHK "おかあさんといっしょ"でおなじみのキャラクターが登場する、好評ツヾソコン絵本シリーズ
