From The TimeSplitters Wiki

Chastity Chased
Game	TS2
League	Amateur League
Section	Mode Madness
Mode	Regeneration
Map	Compound
Character	Chastity
Enemies Encountered	Sadako
Rewards	Silver: Regeneration
Medal Requirements	Bronze: 10 Kills Silver: 10 Kills in 4 mins Gold: 10 Kills in 3 min

Based on the Story Mode Level, "NeoTokyo" This is a one-on-one Match with Sadako!

Briefing

Chastity is honing her combat skills in a simulated shootout with Sadako at the Compound. Virtual health Regenerates so you should hold back if your wounded. The same applies to Sadako - so persevere to score kills.

Strategy

If you look at the requirements for each medal, you'll see that this ,match looks very similar to Adios Amigos, so you should make some easy kills, if only that were true. Since there's only one other enemy here, Sadako, it will take a while to reach 10 kills within the requirements for a gold. Concentrate on locating Sadako and a good weapon and ammo to increase your chances of getting a good medal, the Plasma Autorifle is a must for this level!