Mayoiga no Oneesan The Animation

Both anime are about a young boy (shota) who meets two girls and starts having sex 

Both are about a cute shota having lots of intercourse with two sexy onee-chans, for both first episodes, the second one of Cherry & Gal's involve another shota and onee-chan, but it's still the same sub-genre. 

Both are hentai that are about shotacon material, doing it with big breasted onee-sans of course, one boy and exactly two girls in both of them, you don't need to know anything else. 

MonMusu Quest! Is obviously all about monster girls, Mayoiga No Oneesan only has the use of the word Mayoiga as something fantasy related, but it's only the use, so it's completely mundane instead, but if what you like about MonMusu was the shotacon on big breasted onee-san aspect, then Mayoiga is completely about that, these shotas cum gallons, man.