Summary:
Ayumi is a visually stunning map IMHO, and I think this map plays very well, but it can easily become one sided if a team does not play aggressive.
Key Points On the Map:
Cold Turn: This is a great location for an outer base. With easy movement to pressure hive, and the ability to siege Hamasaki, this is a key location to try to hold.
Eastern Entrance: Much like its cousing Cold Turn, you can easily get to Hamasaki and AE35 hives with a short walk.
Siege Positions:
All siege positions below have been combat tested for accuracy and ease of defense. The sieges in the picture below are placed AS FAR AWAY FROM THE HIVE AS POSSIBLE while still reaching.
Pressure Control Hive:
Siege Point I:
Approaching the hive from Marine Start, this position is sometimes difficult to hold unless you weld the vents behind you to keep aliens from flanking you. You can actually set up a phase gate against the Server Outlet node, but it's a short run to the TF, which can make for a problem. MAke sure to build the TF and sieges on the platform area, gives your marines more maneuverability. Also, place at least one turret where it can shoot under the PG. Elec doesn't work properly on ledges sometimes and a skulk could bite the PG from underneath it unharmed. There are weldable vents behind the outpost and one vent that comes out right above the outpost from the hive, so watch for gorges and lerks there.

Siege Point II:
If you are moving in from Cold Turn, this is a good place to set up siege. By building the TF/PG on the corner, aliens must risk themselves more openly to attack. Placing the sieges against the other wll gives your marines a clear hallway to shoot from. There is a vent behind this location from Server outlet, so watch for flanking aliens. Also, there is a vent directly above this location, so keep a gl spamming in there, or keep your eyes on it for lerks, ambushing skulks, or bile bombing gorges.

Hamasaki Hive:
Siege Point I:
If moving from Pressure Control hive, or sneaking in from Eastern Entrance side, this is the prefered location to siege from. You can build all the buildings IN the Resouce towere room and keep it protected by electrifying the RT. Even the sieges can go inside. I recommend placing the TF in the back of the room behind the RT, where it is most protected. Place the sieges and PG in a way that the elec from the RT will reach any alien attackers.

Siege Point II:
If you are moving in from Marine Start or AE35, set up a PG against the node in Eastern Entrance and build the TF in the corner by the hallway. This is tricky because you will have to go around the corner to build the sieges, leaving your team more vulnerable. PLace the sieges against the wall nearest Eastern Entrance and pack them tightly for aliens can be pickked off by LMG fire. If the resources permit, drop a turret or two to protect the sieges, and have the marines focuse mostly on higher lifeforms and protecting TF.

AE35 Hive:
Siege Point I:
This location is an easy walk from Marine Start, and has two automatic doors behind which can alert you to something coming from behind. There is a vent directly above this location that leads to the hive, so be wary of lerks/gorges/skulks. The TF does not need to be around the corner, so place it back near the door so aliens have to be vulnerable to attack it. Place the sieges along walls and in corners to keep a clear line of sight.

Siege Point II:
Most people hardly ever siege from this location because early game point one is better, and late game you can easily GL spam the hive. But if you do siege, you can build the turret factory further back against the wall in the other hallway, and buld the sieges around the corner. That way the TF is more secure, and marines can focus instead on the hive and getting the sieges up. You could actually just run fromt he PG in Eastern Entrance if you have it instead of building another PG.

I hope this guide will help you better understand this map, and you can become a better commander and marine. Please, if you know of any added strategies regarding shotgus rushes, relocation, even well used chamber placements and skulk hiding spots, add them. Let's make this a comprehensive strategy for anyone new to commanding to this map.