First of all, english is not my main language, so don't expect much of me.

the game that steam provide isn't complete, you need a patch from kaguragames's website (at least for the time this guide is being made). It's free so don't worry.
link: https://www.kaguragames.com/product/rebf-patch/

---SPOILER ALERT---
This guide was made just to lighten your game experience and is full of spoilers. Feel free to correct me or comment your doubts.

It's just a turn based 1v1, the things that you need to keep in mind are:

Erogenous Zones-
this will determine the damage she will take from your skills, 0.0 is no damage and 2.0 is doble damage, the skill MONSTER INFO will help.

AGI-
Basically, the one who has the highest, attacks first (even if you have the option of act, the enemy can just attack first) at 50 - 80 and 99 you will gain 1 extra basic attack (thanks "Crusaderboy1" for the info).

Rival's clothes-
This won't be important in the earliest stage of the game, but this can reduce your basic attack damage to 0. Lucky you, the game have some ways to undress the rival, the most common is just halving the enemy health bar.



Steal is another way, you can steal the enemy's panty (it has to be the only clothes she has for you to steal it).



And the best option (personally speaking) is the skill PANTY RAID (you need 50 DEX or more to do it, unless you have BREACHING TECHNIQUE) however, sometimes take some turns to be successful against bosses.

Guard-
There are some attack that just one shot you, usually will be the special attacks, make sure you can endure the damage or just guard it.

Cards-
Very useful in combat, there are some cards that are just OP and will make your build truly shine.

I wanna be the very best. like no one ever was. to catch them is my real test-
Literally, you can catch all monsters in the game (well... almost everyone), i really enjoyed this (mostly). The premise is "simple", you need to undress her and halve their health bar, then use an EGG BALL (the NPC "client" will sell it when you buy the house). They can help you in battle, their ASSIST not consume your turn and some of them are really powerful (some can evolve).
Note: an evolved version of any monster is far more powerful than a captured one.



The capture chance is just RNG (i thought that was an quick time event, i'm a dumbass xD) (thanks "sad pee" for the info)

Blacksmith (Kiven)-
Here you can upgrade your weapons or armour and also exchange/combine materials.

Merchant Guild (izlubelta)-
Here you can trade panties for P points, also if your collection is great, one of the NPC will give you prices. In the shop, the only thing i really gave use is the SUPER EGG BALL.

Department store (izlubelta)-
There are some NPC, but i highlight the card shop that has the Will'o card/Assault ninja card, OP cards in early.

Brothel (Mozeccs)-
Basically you provide service to the ladies and get paid (you need EXP to give them). Note: the first time you complete each one you will recieve a bonus Jenys, it's not much, but can help a bit.

All of the Syrave service attendants (all dungeons)-
They give you some info of the dungeon, heal you (cheap) and the first one in the dungeon will offers a premium booster (2x EXP obtained for a period of time). also you can "Register warp location", once registered, you can teleport back with the help of the Guide, good if you want skip the dungeon (thanks Crusaderboy1 for the info).

Blacksmith (orc village)-
There are powerful weapons to craft here (Ogre fang is my favorite).

Sif (syrave Adventurer's Guild)/Epsilon (orc village)/Eris (Orgue mansion)-
These fights give some EXP and good loot

Guide (all cities)-
They have a special shop with items that can help you advance faster.

In your house, you can use you bed to rest or spend some sexy time with NPC.

Instructor Sif-
She is in Syrave aventurer's guild, going down the stairs, she gives you some tips and then you can fight her, she will mention that is looking for a bow, craft the THIEF BOWGUN and give it to her.
Note: the GOLDEN EXORCISM ROD is dropped by Nine-tailed cat.

Eris-
Just follow the story, it's a mission.

Valkyrie-
This is a hard one, if you say "i want to **** you" she will tell you to fight every monster (including her with all her strength).

Lisa Himmelgahn-
You have to use the memory crystal and see the defeat scene without underwear, pick the "become Lisa's sex slave" and that's all (thanks Crusaderboy1 for the info).

Receptionist-
The NPC that give you P points will give you a special item if you hace a fine collection.

Pisca-
Just follow the story.

talking to some NPC or in some dungeons are "secrets" this is what i found.

Undersea temple-
In one grave it's the code 37564, IT'S A TRAP! overwelming enemies just to duck you (thanks Crusaderboy1 for the info).

Sphinx ruins-
In 3F, the puzzle, if you complete this with the color RED, you will fall in a mortal trap, there is a weapon here but beware, you can't teleport and the Laminis won't let you escape (you need to prepare first for this).

Heimdall Dungeon-
Here you need a special key to access, there will be a chest that only a true loser can open, you need to lose against the Warden, she will torture you and capture you then just open the chest.

Kiven Dungeon-
One orc will tell you that he is looking for a card, if you give to him, he will give you an advise. In the dungeon 3B, go to the 3 graves and put the GHOUL CARD and if you have the GHOUL HAT, it will be upgraded to DEMON'S GHOUL HAT

To complete the mission that Pisca gives, you need the skill LIGHT UP to capture the guy.

To capture the monsters "?" and "Unknown" you need the skill LIGHT UP. they will appear as Will'o and Stinger respectively.

Once you complete the Story, you can talk to Pisca and fight Founder Julius (the most difficult battle i dare to say)

Go for the MONSTER INFO skill.

The Dropling card gives you +20 LUCK and +15% drop rate, perfect is you want all drop info.

In Southern plains there is one NPC that trade EMPTY BOTTLES and give 200 Jenys each.

Investigate everything, there are some decorations and NPC that give items.

Take advantage of enemies that are easier to steal panties, the SUPER EGG BALL will be handy.

You can send to farm your companion, it will give you JENYS.

Take the boat to Izlubelta, a bridge will appear to travel for free later.

Focus your status points in a play style, it's better than distribute equally.