1) Outside of story bits the only chara interaction is sex for now.
2) Combat has 2 attacks for girl and 3 for man, space for light attack, F for strong attack and R[ape].
Light attack is universally meh unless you one shot enemies though at beginning it might be good to simply attack>walk away>attack>walk away enemies.
Strong attack depends on weapon and yours is whatever, you can craft better wep later on but instead go to centre of island,
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there are ruins when after you do story bit with girl you will gain access to dungeon where on 5th floor boss has a chance to give katana in chest and as we know weebjutsu is the best thing ever so it will easily carry you through almost everything. To restart boss battle you have to leave dungeon and reenter it from the start so it's painful process depending on rng.
Just don't forget to craft repair kits, these weps come almost destroyed.
R is a special for man, you can use it on women to break their white meter and either rape them or collect them for taming.