In my view this is a good manga, that centres around its main setting while maintaining a good amount of standart entertainment one would expect from a slife of life manga.
Its main points are: elegant and interesting edutainment of survival skills, realistic survival setting on an isolated island, multi-leveled progression, nice slow-paced slife of life content with a good balance of novel and standart situations.
Some of its weaknesses include: Lack of interesting overarching events, few character insights, character and interactions are simple and often stereotypical.
People that like slow-paced, peaceful slife-of-life mangas in an island setting will be happy with this one. Also people that are
interested in learning about survival situations without being proficient at it.
People that want an interesting story, character progression in a personal emotional sense or just a very good episodical slife of life manga might be dissapointed, since this are not its main points.
I will look into the various aspects of this manga, that I think are done fine and explain why I think the flaws it has are not of importance considering its positive points.
This is primary an edutainment manga. Edutainment is aimed at teaching in an interesting and entertaining way. Therefore this manga contains a lot of explanations of survival skills or similar things. While this might sound a bit strange to some readers, it is done in a very elegant and intuitive fashion. The elements that are introduced always serve the situation and are explained simple and straightforward. Never does it feel like the manga tries to teach the reader something without a reason within the story or setting. The explanations also are easy to understand while being as precise and rightful to the science as possible. People that like being teached in an interesting fashion, that does not feel abstract and is based on actual situations will be very pleased.
2 Character and story Progression:
This one is a bit difficult to explain. If you just look at the surface then it might seem as if there is not much character progression going on. The four girls all feel very standart apart from the main MC and it is not given much insights into their emotional state. Similar there are not many events that evolve the story and it seems like the situation of the girls in the end is only marginally different from the start. Therefore one could think this manga lacks progression all in all. This is not the case. There are four main types in which the manga progresses its story and characters.
(1) The progression starts with a materialistic aquisation of goods and improvement on the skills of the party. In the beginning the things the girls find or make are often important for the following chapters. These materials and equipments give them the possibility to do new things or focus on new plans (like searching the island instead of gathering food). New equipment and activities mean new skills to learn (2). In the beginning this is mostly done by instruction from the leading MC that is versed in survival situations. It evolves soon enough into a state where the other girls are confident in their own capabilties and are able to do standart survival stuff by themselves (gathering food, collecting water). Also they are more and more able to acquire new skills by themselves without homares instructions and change the dynamic of the part accordingly (By doing some funny girly stuff and other things, that Homare would not insist on.). With this the progression changes from the skill and material acquisation to the organization of the party.(3) Questions like their aim and plans become important and the priorities that they have (do they want to separate to increase their chances of being found or do they rather want to stay together?) (4) This also is accompied by the personal and emotional state of the main character that resembles inner growth. Homare is no longer alone and learns to enjoy various activities with the other girls even if it is sometimes not optimal for a survival situation. Personal and party progression are more often in the centre and the manga is able to progress on multiple levels without only being concerned about one thing at once.
This change of progression is in my view well done and feels natural. In many moments i ask myself about the kinds of food, equipment and skills they currently have and about their their current goal and overall fittness of the party. Maybe this is something that people that are not interested in the setting will not be able to cherrish, but in my opinion it is unique and very interesting for people that do so.
Still this does not mean, that the manga itself does put this things in the focus explicitly. Many of this progressions are not apparent without thinking about the previous chapters and the overall situation of the party. Often it is only briefly noted that the party now has certain goods or skills that allow them to do new things. So this kind of progression could be more transparent and it might be better centred more openly. So it is not surprising that some readers might not see any progression at all.
3 Overall balance of content:
Besides this progression there is a good pacing of comedic and dramatic moments (Like a person going missing or a person getting sick). It never feels rushed or out of pace. And the story does not progress solely around this events. And this is a good thing since the manga does not forget its core premise: Which is the slice of life aspect of a group of stranded girls. It is not a quick story that has to evolve or a problem that has to be resolved. Rather it is slow and steady with a good amount of your average situations.
Of course this means that this is not a manga for everyone. At the current rate there are about 70 chapters and one could summarize the story in a few sentences if one would only include major involvments. Similarly this is not your standart slice of life comedy that is only concerned with giving good jokes and be all cute and silly. It seems to try things it a bit different than some other of the same genre and I think it does this fine.
Lastly one can mention the ecchi stuff and semi-sexualized drawings. Ecchi-stuff is most often used for comedic sitations and does reflect on the difference between normal behaviour and the special situation on the island. Therefore these comedic sections all feel a bit samey. They still can be funny and cute sometimes. I think that one of the good things about them is, that they do not feel important for the overall quality of the manga and do not impair it. Same goes for the ecchi drawings. They never really push the girls over the comfort zone or depicte them in arousal situations. It seems to search for a balance between the situation of young beautiful girls living on an island and the situations a reader would associate with it. Overall I think that the comedy and ecchi stuff are very mild and do not harm the enjoyment of the manga.
All in all do i think that 'sounan desu ka' is a very good manga with a good balance of edutainment content and slife of life situations that come with its situation. People that like slow-paced and more relaxed mangas with a specific setting and some progression will be very content with this one.