Consult these maps for part 8:

After completed the Dark Realm, head outside to the courtyard of the Keep and enter the green door again (the west area where you played as Kaede).

Again, you need to save the soldier to get an item.

• Equipment: Burst Bullets

Keep going until you see a door sealed with level-3 blue crystal. Open it with Raizan. As you appear, you'll notice a soul holder so press O to absorb some free souls. Walk to the next screen to pick up Genbu book. Walk further toward the headless statue, you'll see a red treasure half hidden containing Vision Staff at the corner. This staff grands you an ability to see Fluorites. Remember this room because we'll come back later. 

• File: Genbu
• Key Item: Vision Staff

Exit the room, you'll immediately see a flickering object on the ground.

• Item: Fluorite

Continue your way to the archery range, you should notice a well on the left side a long the way in this passage. Inside is the another moth man who offers you to the Dark Realm. One of the achievements requires you to talk to moth man twice (maybe they are twin? IDK), first one is in the Sentry room whose you already talked to and second one is in this well.

Achievement: Two to Tango

After you reach the archery range, climb the ladder and proceed to the next door. Replenish your magic if needed, enhance your weapons and save your game. See the door with level-3 red crystal? open it then head straight until you see a treasure box.

• Item: Medicine

Achievement: Road Kill
Now cut the rob that tied the battering ram, the battering ram will roll over those Zombie Soldiers. 

Beneath the battering ram is another Fluorite.

• Item: Fluorite

Continue to the next room. There is a giant red ogre (Barabazuu) and 3 of his minions. He is strong, so it is best to finish them by using all of your magic. After you defeated the mini-boss, look around for 3 items here.

• Key Item: Statue Head (a treasure box in the corner)
• Item: Bullets (a treasure box in middle of the yard)
• Key Item: Decorated Sword (It stuck on the ground, pick it up)

Go back to the room with the missing head statue.

Use the Statue Head you just picked up early to deactivate a trap door behind the room. Circling around to open a treasure box.

• Equipment: Matchlock

That's all you need to do in this part of the temple (west area) so it's time to explore east area.

Go all the way back to the courtyard. Along the way, you will see another Fluorite on the ground.

• Item: Fluorite

When you reach the courtyard, walk around until you see a wooden door, a small scene will automatically trigger. A little inside, you'll see a Decorated Sword shape on a stone, stand near the stone and use the Decorated Sword in the menu to open the pathway to the East Garden.

Kill those Three-Eyes then walk toward a green sealed door and open it (ignore the left turn for now). In this room, go straight to the outside, you'll see a draw bridge (if you press X, it will tell you that with the right tool, you can lower the bridge). All you have to do is equip your Matchlock you just obtained with Burst Bullets (Arrow and normal bullet work too but you have to aim precisely), then shoot the robe on the other side. 

Cross the bridge to open a treasure box for Bullets then cut through the paper on the wall to reveal Talisman.

• Item: Bullets
• Item: Talisman

Now turn around, cross the bridge, then turn right. Examine the door to pick up a file.

• File: Journal #6

Press X again to enter the door. Go straight pass the first door to the left and enter the second door. There are 3 items here:

• Item: Bullet (Inside the treasure box)
• File: Genbu (on a table)
• Map: East Area Map (hidden before another hanging paper)

Go back to the first door you just passed. You'll immediately see a treasure box, open it for Bullets.

• Item: Bullets

You don't have to kill the Samurai though, just use the stairs to go up and kill every monster on your way until you reach a ladder with another treasure box.

• Item: Magic Jewel

Climb up to the rooftop to find 3 more items.

• Item: Fluorite (inside at a corner)
• Item: Power Jewel (near a corpse outside)
• Item: Talisman (at the opposite side of Power Jewel)

After everything is done, go all the way down where you picked up Bullets, kill the Samurai if you want. Under the staircase is a door sealed with wind crystal level 3. Open it, you will appear outside of the building and a Three-Eyes is waiting to greet you.

Achievement: All Lives Big and Small
don't go anywhere yet. Notice 3 fish in the pond? Stand on water and start holding O (absorb soul) even though there is soul. Wait up to 1 minute, one of the fish will start emitting a yellow soul. 

Head to the next area, kill cloaking demons then absorb some free souls. Continue your journey until you reach a waterfall.

Achievement: See You Next Fall
Here you'll see 2 Samurai (one on the other side, another one is behind the waterfall), now lure them one or both to the middle of the bridge (the achievement only require one Samurai). After that, walk away to any side of the bridge and cut the robe, easy kill right? And don't forget to absorb their souls.

Now, behind the waterfall is another puzzle box.

• Equipment: Great Armor (Solution: bottom-left, top-right, bottom-right, bottom-left, bottom-right)

Equip it immediately and proceed to the next door. This room has a Magic Mirror, a puzzle box, and a normal treasure box.

• Item: Magic Jewel (Solution: 3rd, 6th)
• Item: Medicine

Save your game and go downstairs you will see a flickering object, it is a Fluorite. 

• Item: Fluorite

See a boat? board it to cross to the other side and enter the room. Walk to the end of the room to pick up Great Bow.

• Key Item: Great Bow

Enjoy a cutscene.