since he has no power or he just goes groveling at the Fox Girl who is coercing him for an idiotic reason like peeping (his situation is already bad enough when the Dryad came up, so why care after that?)

Energy is in a persons blood, but their semen has a lot of it concentrated, so she has sex so she can get lots of energy at once.

#1 My thoughts and opinions on the tree succubi

Alright so tree succubus needs to consume energy in order to live and for (I think) to revive the other dead spirits ...no clue on that ,but the main issue I have been having is here ability to gain power .Sure she can have sex to gain what she wants ,but it didn't seem that that was necessary from how she attacked the mc.So couldn't she have just gained energy (killed ) without intercourse, I'm sure she could absorb their energy through small roots she could grow from her body and drain here victims in that manner ?Did she do it because of trying to let them die happily ...but why would she care, she even had sex with the killers (loggers) whom killed all her family *_*Then has no problem trying to kill the MC...and it even seems like she had no problem killing in that manner :/ Alright so at this point she became a tree seedling I think also she instead of using less power to kill using her natural abilities aka roots (she becomes more plant-like when she lost her energy )which she displayed fighting MC to directly enter all parts of the bodies that means she can take semen and blood at the same time not expending enegry on maintaining a completely human body !
#2 Fox woman ...I'm not good with names so bare with me
She is thousands of years old (catch a hint !) she served or loved the past him who saught immortality and I think in a way received it .So thus she has been waiting for him to be reborn (some commitment ) ,reason I say this is because he has a lot of potential power (like a battery ) but she doesn't kill / rape our mc I'm talking about our black haired girl ...so can anyone guess what she want him for or is she just guiding him on the path to remember his past self and gain power to be with her
#3. The MC

My guess is had the same soul as the past guy who saught immortality and when reincarnated didn't have has soul completely~wiped /cleared~(reincarnation is a head ache (usually )ps you can't avoid the soup !) meaning he has a link or memories and powers of his past self .Also mc is broke and going to college and all this is going on all of a sudden not before there...Finally on top of that anytime during the past he could of almost died and unleashed that power and would be able to see the creatures through glass so Fox lady must have known about him somehow for a long time I think....
#4 (Funny )Black haired girl
She really is what makes the story funny usually she is a secret agent of some sorts and is sent to either have sex with the mc or get his semen maybe both ...but but she is innocent ...drugged the mc got lube and took of his pants and couldn't go any further and broke out of a window :D MC got cought with his pants down and was unable to speak or in any way explain it ! What organization do you think she works for?

#5 the monster hot spot
So many monster are drawn to one area it must be significant to the story and the MCs power.