I am Dr Soumen Patra and try to solve your problem.
One thing you have to know clearly that two areas ie. pubic area and axillary reg(underarm) are generally darker due to hyper pigmentation and coarse thick hair.It is quite normal & natural thing after puberty
and it does n't depend on your fairness of other body parts. In 90-95% women,those area are darker.
Here I give you some tips to reduce darkness of PUBIC AREA (Vagina):
*Don't wear polyester or synthetic underwear.Use cotton underwear and always loose fitting.
**Regular (weekly basis) shaving of your pubic hair with hair removing cream. Occasional waxing may be needed.
***Bleach the area with lemon/lime juice (Natural Bleacher) and leave it for 20 mins. Try shower to shower.
****Keep the area dry and clean all times.Use toilet paper after each bathroom work and after every bath, apply corn
starch to the area to keep it dry. Avoid using talcum powder.
*** Your inner thighs rub together & this also causes darkness,you may need to lose weight on your thighs.
**Make a decoction of a teaspoon each of milk powder, honey, lemon/lime juice, and almond oil. Apply on the area and wash after 15 minutes.
*Maintain a healthy diet and use only sanitary napkin during periods.Also maintain your personal hygiene,sleep timely and keep tension free.
You have to continue above things for 3 to 6 months.Then you may get a good result.
All the best.