Generally speaking, constitution will affect your HP, Intelligence your magic-based stats, Strength your attack power, Speed your accuracy and evasion rates, and god knows what Luck does, but it's probably worth spending points on. However, over long-term development, these rules blur a bit.

You start the game totally unequipped, so it's probably a good idea to equip yourself before you head out and face the demon hordes.

There's also a Jakyou Manor to the top right of the floor. You can always tell a Jakyou by the man in a blue dress.

Before you go and fight evil, you may want to see what the real world looks like. Go to the Elder's place (the L-shaped "building"), and pick the first option. You'll be taken to the underground shelter your character lives in. Encounters:

Kid
"Big brother, are you going out to explore?
I wanna go too..."

Soldier
"The surface world isn't easy like it is in a game!"

Man in sunglasses
"Oh, it's Tatsuya.
How're you?
If you beat Devil Buster, I'll give you 750 makka."

Pink Girl
"I couldn't even think of leaving this shelter.
The surface world is full of demons!"

Girl
(Shiro's girlfriend, Hiroko's room)
"You're always together, aren't you?
I'm a little jealous.
Hey, Tatsuya... who's this "Yuki" in Devil Buster?"

Weapons Guy
"Our world is being destroyed because of the demons.
This shelter should be safe, but this place is equipped so that when, if by some chance, a demon appears, weapons will be secured here.
Come here if something happens."

Girl
"The bar is full of knowledgeable people.
If you treat them to a drink or something, they might tell you something."

The Poison Bar:

Barmaid
"Welcome!"
-Talk to customers
-Order food and drink
-Leave

The choices for the first option are "Young Man", "Long-haired Girl" and "Suspicious Man".

Young Man
"It seems there are even some towns outside.
But, there's nowhere safer than here."

Long-haired Girl
"Oh, are you treating me?
I want a Super Milk."

She'll get mad at you if you refuse or can't afford it.

Suspicious Man
"There's an infirmary on B3F, you know.
Don't you think the nurse there is cute?"

The drinks you can choose, should you pick the second option, are Super Milk and Miracle Tonic. However, you don't have the money to sit around drinking instead of saving the world at the moment.

The elevator on this floor is out of service, so rather than checking out the nurse on B3F, let's go back to the computer room. You'll get three options:

Selecting Devil Buster will bring up the following text:

"Devil Buster... ... ...
Load complete, starting"

Hit Yes and you'll be back in Micon. Hooray! Go down the stairs, and get ready to start killing stuff. Encounters on this floor:

Man:
"As the moon becomes bigger, the demons get wilder.
During full moons, please be careful as they won't even be able to talk."

Man
"Minion have their own special skills, but whether they use them or not depends on the circumstances at the time."

Room
"There's something written on the wall...
The one with exceeding intelligence art one who withstands magic;
The one with exceeding luck, the one who is protected by the power
of the gods, and is protected from diverse hardships by an unseen hand"

Woman
"Minion don't level up!
You power them up by fusing them at the Jakyou Manor.
By fusing Fire/Wind/Earth/Water Slimes or Salamander, Sylph, Gnome and Undine with a demon of the corresponding race, you can increase its rank by one level.

Man:
"The guys in the front of your party are tough!
Enemies will come aiming for the front!"

Man
"Magnetite is the source of the demons' energy.
When summoned demons eat up all the magnetite, their HP will be reduced instead, so be careful!"

Room
"The Orb of Silence lies inside the Minotaur."

In one room, you'll be greeted by a demon.

Demon "I've been waiting for you, brat!"

It's a boss - Jaki Minotaur. He has around 50 HP, and attacks using physical attacks and Mahazio. If you win, you get the Orb of Silence (静玉). Don't forget you can always go back to Micon to upgrade your equipment, buy new items, get healing or fuse demons.

If you go upstairs from the floor Jaki Minotaur was on, you'll find another room.

Room
"There's something written on the wall...
Offer it to the statue of the evil god!
Offer the blue light of the Orb of Silence!
Listen, seekers! Listen to the sound of the storm awakening from the edge of deep slumber!

In another room, you'll find a statue.

Will you offer something to the statue of the evil god?

Picking Yes will take you to some more options:

Picking the first option will result in nothing happening. (Idiot.)

Picking the second will result in the following:

Tatsuya offered the Orb of Silence to the evil god statue.
The evil god statue absorbed the Orb of Silence!

"I am Maou Pazuzu, born in the midst of flame and storm...
Now, released from the seal, I will leave here with the light...

My saviours...
My name is Pazuzu.
Under the orders of God I have come to give you an important mission.
At the end of the 20th century, the war obliterated the world's civilisation in an instant. Now, 35 years after the great war, humanity is being threatened by a fearful enemy.
One after another, the demons came into this world through the dimensional tear caused as a result of the war.
That split is here in Tokyo.
When I descended to this land as a messenger of God, I was sealed into a computer by Maou Bael, who rules Tokyo. You are the ones who saved me from that.
My saviours, you are not just MY saviours. You are in fact the children of God, who will save humanity from this peril. My duty is to aid you whilst guiding you towards the right objective.

I will give the Devil Summoning Programme to you, Tatsuya.
If you use your computer, you can summon demons you've made into Minion anywhere. I will transmit the demons you've made into Minion in Devil Buster to your computer. I'll also give you the Auto-Mapping Program. Places you've walked through once will automatically be recorded on your computer.
To Shiro, I shall give the spells "Di" and "Mappala".
Because the seal has been broken, the demons coming through the connection to the computers in the shelter have begun to invade. Now, you must go and defeat the Necromancer Nebiros, who has appeared on B1F!
Well then, take care!"

What was that just now?
Tatsuya, who had been playing the virtual reality RPG Devil Buster in the computer room, finally returned to reality.
Barely able to speak due to the surprise, his friend Shiro, who was watching dumb-founded next to him, spoke agitatedly.
"That wasn't a game just now, was it?!
It looks like you've somehow involved us in some terrible situation!
But... it seems it's not like we can just run away.
Why don't we accept it and try being these Saviours or whatever?
First, let's go to the weapons store and get some kinda weaponry!"