One of the interest of Shinobido on PSP is that despite the very sad lack of mission editor 
it's possible to use missions created in the mission editor (that is not removed there) of the PS2 version.
Unfortunately not everyone has a PS2 or the game on it so the "single mission" game mode is devoid of entries.
Fortunately, some people have shared missions and it's possible to install them into PPSSPP
By example there on gamefaqs you have 2 people sharing a bunch of missions :
h ttp://www.gamefaqs.com/psp/929292-shinobido-homura-soul-of-the-ninja/saves
You then simply install all those missions folders into your
..\ppsspp\memstick\PSP\SAVEDATA\
And they will be all available in the single mission mode of the game
(note that you should not expect those single missions to be as good as in the "story" mode , those missions environment are rather corridor and cube based , landscape is rather boring tactically, probably due to how the mission editor works)
it's possible to use missions created in the mission editor (that is not removed there) of the PS2 version.Unfortunately not everyone has a PS2 or the game on it so the "single mission" game mode is devoid of entries.
Fortunately, some people have shared missions and it's possible to install them into PPSSPP
By example there on gamefaqs you have 2 people sharing a bunch of missions :
h ttp://www.gamefaqs.com/psp/929292-shinobido-homura-soul-of-the-ninja/saves
You then simply install all those missions folders into your
..\ppsspp\memstick\PSP\SAVEDATA\
And they will be all available in the single mission mode of the game
(note that you should not expect those single missions to be as good as in the "story" mode , those missions environment are rather corridor and cube based , landscape is rather boring tactically, probably due to how the mission editor works)