Few coloring errors:
Eirin-Reisen is orange, which isn't in the key.
The line connecting Eirin with the Sisters is orange checkered. Again not in the key.
Why is Eirin/Tewi Yellow+Green, while Eirin/Reisen isn't?
Wouldn't call Sanae/Reimu Friendly. Tolerant at best. They are rivals in terms of their shrines.
Cirno's connections make her look like a massive Tsundere. :V
Soga/Futo isn't friendly. They're on bad enough terms that Futo killed Soga and is the reason she woke up as a ghost. They only work together because they both work for Miko. If anything, they're hostile to each other.
Seiga has the same line to Miko as Eirin does to the Watasukis, which isn't explained by the key.
Reimu isn't friendly to the Fairy Trio, Tolerant maybe.
As shown in SA, Aya is familiar with who Yuugi is, from the time the Oni ruled. I think IaMP does the same with Aya-Sukia.
Tokiko, her only appearance was apparently working for Rinnosuke, so should have some connection. She should probobly be listed as familiar unless she was explicitly stated as an employee, however.