After the chapter prologue, a menu will appear which allows you to select a partner, equip a jewel, equip items, and view the Koukan points ranking.
Inuyasha, Kagome, Miroku, Sango, Shippou.
Lapis Lazuli Jewel - Increases physical strength (hit points) by 10.
After you select which character you want to use etc, choose the last option to go to the map/barrier. You will be asked for confirmation, choose the first option (Yes) to start the game, or choose the second option (No) to go back to the menu.
After the opening dialogue, you will be shown the objectives for the chapter.
Collect all the Shikon shards.
Your partner's hit points drop to 0.
Your initial goal is to defeat Rouyakan who has the Shikon shard. However, if the Peach Man defeats Rouyakan, the following dialogue will appear:
Peach Man: Wahahahaha! I have the Shikon shard!
Peach Man: Now, I'm going to eat you all!
If that happens, your objective will change to defeat the Peach Man.
Rouyakan, Peach Man, Kagura.
Rouyakan will randomly wander around the field, though he tends to head towards the Peach Man for some reason. He has no items so he shouldn't be too much of a problem.
The Peach Man will head towards Rouyakan in the beginning to take the Shikon shard. If he succeeds in getting the shard, he will then come after your character. The Peach Man also tends to use items which force you to miss a turn, and he also sets traps. In battle, the Peach Man will use items to recover hit points.
Kagura is on the opposite side of Rouyakan in the field, so the chances are that either you or the Peach Man will reach Rouyakan before she does. In this chapter, Kagura will not fight the Peach Man, instead, she goes straight through him. Kagura will head towards you and set traps along her path, but I wouldn't worry too much about her.