One of the main themes is identity. The characters often struggle with who they really are. For example, some characters have different personas in different 'worlds' within the story. Another theme is friendship. The relationships between the characters are complex and often crucial in dealing with the various challenges they face.
There are quite a few Kagerou Project light novels. However, the exact number can be a bit hard to pin down as new releases might occur over time. Generally, there are several volumes that contribute to the overall Kagepro story in the light novel format.
Well, without more information, it's hard to say precisely. Generally, visual novels can cover a wide range of themes. 'hara kano visual novel' could be about the experiences of its characters, maybe their personal growth, or it could center around a particular event or series of events that unfold in a fictional world. It may also incorporate different art styles and narrative devices typical of visual novels.
Well, 'photo kano visual novel' is probably a story - driven experience where the visual aspect is important, just like other visual novels. Maybe it has a unique art style to depict the world of photography. It could be about a young photographer's journey, his or her growth in the field of photography, and the relationships that are formed through the shared passion for photography.
A fanfiction might explore a scenario where Kido and Kano have to work together to face a new threat in Mekakucity. Kido's calm and collected nature could complement Kano's more mischievous but also resourceful personality. They might start off bickering but as the situation gets more serious, they realize how much they rely on each other and develop a newfound respect.
Since I don't have detailed knowledge of the 'photo kano visual novel', I can't give a definite answer. Generally, if it adheres to common standards of family - friendly content such as having a positive message, no inappropriate images or text, it could be suitable for all ages. However, some visual novels are designed with a more mature audience in mind, so it's important to look into reviews or more information about it.
One common theme is friendship development. Since they have different personalities, seeing how their friendship grows is a popular topic. For example, in many fanfics, they start as acquaintances and gradually become close friends.