Just don't tell them, or they'll fire Meiling

Yuzuna said:

Now then, what kind of place do you suppose Akyuu-chan's house is?!

A theme park with rides, including a roller coaster that takes you past scenes from the Kojiki and all the eras of Japanese history.

There's plenty of guards around. SDM is just the only place that has a gate to guard.

Gate Guards are the things of the past these day.
Nowadays, we substituted front door security with a tough-as-heck door that only opens to the right person. Slightly futuristic settings even have those cameras with machine guns attached to them.

Lt_Col_Summers said:

Gate Guards are the things of the past these day.
Nowadays, we substituted front door security with a tough-as-heck door that only opens to the right person. Slightly futuristic settings even have those cameras with machine guns attached to them.

if someone really wanted to get into the Hieda estate they'd just fly over the gate. Though I would imagine ther's some fast acting security measures (Keine, Yukari)

This is the perfect chance for a Metal Gear Kogasa strip if yuzuna99 ever wanted.