*This review is for those who have read Silent Sinner in Blue.*
1. We get to see the thoughts of some of the more rarely seen characters.
2. The stories are pretty good and help to explain the motivations of the characters in SSiB well.
1. The Lunarians' stories are less exciting and may be harder to get into.
2. Like SSiB, CiLR requires the reader to also know Touhou lore.
Silent Sinner in Blue encompasses eight stories, seven of which are from the perspective of certain characters, namely Eirin, Kaguya, Toyohime, Mokou, Yukari, SSiB Reisen and Youmu. A bunch of these characters rarely appear outside of the game they
debut in or Silent Sinner in Blue, such as Kaguya and the Lunar Capital folks. While Silent Sinner in Blue showed us the daily interactions and activities of the various characters, Cage in Lunatic Runagate focuses on the inner thoughts of the characters, such as their reminiscence of the past or their thoughts on the events of Silent Sinner in Blue. As such, Cage in Lunatic Runagate provides valuable insight into the mysterious lives of a number of these very old youkai and Lunarians. We get to see how Yukari schemes, how Kaguya spends her time, how the Watatsuki sisters prepare for Remilia's imminent invasion of the moon etc. Such an opportunity for character development for these characters may never come again in the future of the Touhou series.
The next point is closely linked to the previous one. A number of the stories are very enjoyable to read. Mokou's story is very touching and Youmu's is silly and comedic in particular. All chapters except 2 and 4 (Kaguya's and Mokou's) have a large focus on the events of Silent Sinner in Blue and help to explain how each of the characters react to the various events, like how the Eientei folks respond to SSiB Reisen's initial arrival on Earth and how Youmu awesomely fail at spying on the Scarlet Devil Mansion crew. Ultimately, it shows how Yukari's scheme comes together and how the rest get entangled in her plan.
However, not every story is particularly exciting. For instance, the first three chapters that follow the Lunarians can be a little uninteresting at times due to how long each chapter is but these three chapters are full of reminiscing. Flashbacks may be informative, but they aren't always interesting. While the new information about these characters are appreciated, the recollections make the chapters feel rather drawn out. Even as a sucker for Touhou lore, I felt reading these chapters a bit of a drag compared to the rest of Cage in Lunatic Runagate.
And of course, being complementary material to supplementary material to the Touhou series, Cage in Lunatic Runagate requires its readers to be equipped with prior knowledge of the Touhou games up to Imperishable Night, on top of the story of Silent Sinner in Blue (which requires Touhou knowledge to understand in the first place). For non-Touhou fans, this novella will be even more confusing and boring than Silent Sinner in Blue due to Cage in Lunatic Runagate delving even deeper into the Touhou lore.
In conclusion, Cage in Lunatic Runagate is an excellent source of Touhou lore revolving the cast up to Imperishable Night and in Silent Sinner in Blue. However, being a novella and going so in-depth into the Touhou lore, it is a lot less fun than Silent Sinner in Blue. Cage in Lunatic Runagate is for the Touhou fans who love to know more of the lore and have the patience for massive walls of text.