I’m currently trying to get S-Ranks on the first playthrough, following various promising strategies and tips I’ve read in this board. I hope it will help in case you plan to play it from the scratch too.
Note 1: Load Suikoden IV data, it will make your life much easier!
After the tutorial fights you can spend money and skill points, but be careful not to waste anything. Hone your weapons (but not those of Andarc and other mages), attach fighters an elemental sword rune, buy some equipment if you can afford it (remember the selling trick: sell equipped stuff for more money). As for skills, Kyril needs battle lust and extra-move, Andarc needs lightning magic and extra-move (and godspeed later), Seneca needs sniper, battle lust and extra-move.
1) A Chance Encounter At Sea
The first time I failed because I lost too much time dealing with the pirates. The second time I used Andarc and Walter to go straight for Sigurd and succeeded. Don’t forget to let Andarc and Seneca talk to each other to learn the Cohort unite attack. I think I didn’t get the bonus item, but it’s not that important. After the battle unequip Walter and give an earth bead to Andarc (or buy one for Andarc).
2)The Night Sea (2nd Battle)
Move Brandeau in between the 3 pirates and kill the right one, move Edgar forward to kill the pirate left of Brandeau. Move Andarc towards the others and lay an earth bead on Peck. Next, try to kill the pirate axe (who has beads equipped) with Brandeau, and move Edgar in Steele’s magic range and lay a fire bead. On the next few turns bring Andarc closer to Steele to finally cast the Thunder Runner on him, then finish him off with Brandeau or Edgar. I didn’t care about the Jolly Pirates, there were killed and the enemy started attacking Peck who was well protected by the earth element.
3) Back Streets of Razril
Easy. Just smack them. If you succeed, try to beat Rita (“Game on!” quest) by 1 tile to get the Star Earrings (not necessary, but why not). Equip Kyril with 3 Flame beads (he has a fourth one more from the rage sword rune) and 1 rage bead. After your fourth turn count the tiles and lay your last bead so that you have 6 tiles more afterwards. Rita usually puts her beads on empty spaces. After recruiting her, hone her weapon, give her the battle lust and extra-move skill, and a thunder sword rune if you can afford it.
4) Underground Path
Just be quick, learn the Dying Wish attack along the way to the stone obstacles. Only use one of the unite attacks on at least 2 enemies (save the other unite attack for the next battle). Forget about the chest, destroy the stones, kill the next wave, and try to slip through the enemy lines (I used Kyril). Enter the exit area as quick as possible; in my case at least 5 enemies were still alive, but I got S-Rank. Equip Andarc with the Archmage’s Glasses.
5) Secret Chamber
Use the other unite attack that you saved on as many enemies as possible, 2 at the very least. Don’t open the chests. Equip Andarc with the Archmage’s Robe.
"Within the four seas, all men are brothers" Shuihu Zhuan