The furniture system is a feature implemented in version 0.31, to give you more options of increasin the affection for you girls. The player is able to add furniture to their mansions in order increase the lifestyle happiness for the harem.
Most furniture can be bought in-game or obtained as quest rewards. All characters either like, love, hate, or don't care about any specific piece of furniture. As a rule of thumb, bought furniture only gets "like" while quest furniture gets "love" or "hate" responses.
The following passages are only for those who want to use furniture as a mean to gain relationship points for certain harem members faster. If you want to use furniture for decoration, you're free to do so without any negative consequences, the following rules are only for optimizing purposes.
The amount of happiness a piece of furniture produces depends on the house it's set up in, the location inside that house and the person you want to influence. Harem members who stay in one location like Alina or Pandora are only influenced if you place furniture in their respective homes, while party members who travel with you from house to house are effected by all the houses. For example, Gargan usually likes the Eastfort Condo most, since that house has Sword Stands, Spears and Axes, which are all object she likes. If you place other items she likes more (like the Guild Banner or the trophies from the tournaments) in Northmarket Manor, she will now calculate her happiness from Northmarket Manor from that point on.
Not every piece of furniture has an effect on every person, even in the right house. For example, Bronwyn will not care if you place any of the trophies up or not, no matter of the house or location.
Even if you place a piece of furniture in the correct house, it can still have different effects on each person. For example, Penelope likes Palm Tree in general. If you place one in the front hall or the lower west wing, where the bedrooms are, she will still like them. If you place one in the study or Alina's Bedroom, she won't be affected by the Palm Tree at all. For each furniture a girl likes that is set up in a room she likes, you will gain a bonus of +1 to her happiness at the end of each day, up to a limit of 8 per girl and day.
Certain pieces of furniture cannot be bought, instead you gain them as rewards for certain quests or achievements. These types of furniture have a higher value and certain girls will love them. If you place a loved piece in a room that's also loved, you will gain a bonus of +2 on that girl's happiness at the end of each day. For example, Kyrie loves the Guild Banner you get after reaching the Banneret rank in the adventurer's guild. If you place it in the study in Northmarket Manor, a room she loves, you will gain +2 bonus for Kyrie from it.
Stacking the same item is ineffective as well, each piece of furniture will only count once per house. This means you can place a keg of ale in Northmarket, Westcastle and Eastport and it will work there each time, but placing three in Northmarket will only count as if you placed only one.
Using the following charts, you can first check which type of furniture the person you want to influence likes or loves. On the charts below those, you can find out where to place that piece of furniture for the best effect. For example, if you want to boost Orange Girl, you'll see she loves the Guild Banner and likes the clock, the keg of ale, Palm Tree, Begonia, Schefflera and Monster Deliciosa. Looking further down, you see she is only affected from furniture in Westcastle Manor, which makes sense since you can only find her there. Inside the manor, you see she likes different places in the manor, like the kitchen or the main hall, but she loves the study. For maximum effect on Orange kid, you should there place the Guild Banner in the study of Westcastle Manor. If you want additional happiness for her, you can place a keg of ale and a Monster Deliciosa in the study as well.
Please be aware that some piece of furnture can negatively effect people as well. For example, Chimei hates the Dragon Head Trophy, so if you don't want to make Chimei unhappy, either don't set up the Dragon Head at all, or in a room she doesn't care about. A piece of furniture that triggers the "Hate" emotion will count as -1 for that girl's happniess at the end of each day.
In general, furniture you get from quests, like the piano, will work better than bought furniture.
↑The Eastfort Condo comes pre-equipped with 1 Clock, 2 Sword Stands, 2 Decorative Spears, 3 Decorative Shields, 2 Armour Stands, 1 Landscape Painting, and 3 Decorative Axes. These items can be cleared and placed in your other homes if so desired.