Gate Keepers (ゲートキーパーズ), released 12/16/1999, developed by ESP, published by Kadokawa Shoten

This is a franchise that started with this Playstation game but also had an associated manga, anime, and light novel. The anime was one of the last projects of Shiozawa Kaneto, who died suddenly during the creation (he only played a guest character in one episode).
This struck me as a pretty lazy harem product. Neither the plot nor the characters are particularly well developed, and the gameplay is not great either. It’s certainly much better than Seirei Shokan, but I can’t help feeling like they were mostly relying on the harem-series angle to get people interested in it.

The game begins with a vocal song and animated intro (I wouldn’t be surprised if this was reused in some form in the anime). There are other short animated sections as well. Aside from this, the graphics are serviceable.

I’m not necessarily the right audience for this but I’m not sure how much the girls in the game would appeal to harem-series fans.

They look OK but they have this 90s-anime feel to them that’s a bit outdated now.

The in-battle graphics aren’t bad either, although they can get in the way of seeing things — fortunately the game gives you a button you can push to temporarily take away all the graphics so you can see where everyone is, although even then I sometimes found it hard to tell exactly where I needed to move to attack a unit. On the whole I would say this is a decent example of this middle-late period of Playstation games.
For music and sound, there is a lot of voiced dialogue, and the seiyuu lineup is pretty good for the period. One thing that I never like is the lack of voice for the main character — I know this is normal in visual novels and this kind of game (I guess so you can imagine yourself as the lead?) But in all the animated sequences the MC does have a voice.
The story involves a group of “Gate Keepers”, who can call on things from some alternate world to essentially use magic. The main character is an average high school student who is recognized by this secret international organization that gathers Gate Keepers (who of course are all kids, at least the ones in this game) to protect the world against “Invaders”. Each Gate Keeper is associated with a different Gate which sets the type of powers they can use.
The basic story of the game involves efforts by the Invaders to take over the world, that then center on a human named Kageyama Reiji that is working with the Invaders. The game takes place in the late 1960s for some reason, and begins with a scene where Reiji uses his gate magic to kill a bunch of soldiers in the Vietnam War (and the suggestion I think is that this ends the war).

The main interest of the game, I suppose, is the different girls; of course you can develop friendship levels with them and get special endings (romantic, perhaps, although I didn’t get such an ending) with the girl you like the most. As usual, they represent a range of common character types — the shy, morose study girl, a few foreigners, an athletic girl, a child (sigh), an airhead, and such.
The system alternates between the battles and the conversation parts. For the conversation, the characters are all in a school — it’s a real school but it also serves to hide the command center of the Gate Keeper force, so that the GKs can all make it there in an instant if they need to. So you can choose where you want to go in the school to talk to the various girls. Sometimes they might not be there and then you go somewhere else (like the gym or nurse’s room). You might also get a choice of what to do. I don’t believe that going back to the same girl more than once ever does anything but I could be wrong.
You only have a limited number of places you can go (unspecified) before the alarm will go off to send you to the next battle

I didn’t look at a walkthrough to see what choices were good or what I should do. This ended up unfortunately with my highest friendship rating being the Chinese 11 year old (or something) above. Fortunately I did not get a high enough value to trigger the love scene, but I did have to hear from one of her classmates this very creepy dialogue about what is attractive about her. It sounded more like what a creepy adult would say about a child rather than what an actual 11 year old would say.
Once you beat the game you can access an extras menu that shows you a completion percentage which I guess measures how well you did with each girl, and the better you do the more extras (images and such) you unlock. I had 0% with every girl except that Chinese girl who had 66%; I guess I didn’t pick the right options for the others.

There are one or two battles per chapter (the whole game is pretty short, I finished it in 12 hours). Unfortunately you can only send out the main character and at most 2 girls (sometimes just 1). This is especially annoying because there are no free or side battles, so you pretty much have to concentrate on just sending out a core party. So you barely get to use any of the characters — I guess their idea is that you replay it several times (the save slot has a three-digit counter for how many times you’ve cleared the game), but I’m not going to do that. I generally sent out Jun (who has a gun) and Fei (the Chinese girl) because her gate attack could hit everyone on the screen.
Each character has their own weapon; you don’t equip anything but the weapons have different ranges and powers. The MC has both a gun and katana.

The system is player/enemy turn. You can move and act. The actions are attack, Gate, and jump (up to a higher area). The main character can also call in help to heal or status restore — this is unlimited but it takes the MCs turn and because you have so few characters you can’t rely on it to get you out of every jam.

To use the Gate powers, you first choose to open that character’s gate. You then see a number appear over the character — this is the remaining power of the gate. It goes down by 1 each turn, and then every Gate power you use takes some amount of energy (ranging from 0 to at least 5). Once it hits 0 the gate closes and cannot be opened again for that battle. Personally I would have rather seen a system where the gate energy can recover and be opened again — the system as it is seems too limited, especially in battles with multiple sets of reinforcements or when the enemies are spread all over the map. On the whole I think the battle system has good ideas, but the tiny party size and very limited use of the key power of the game makes it feel rather thin. Halfway through the game you get the ability to summon a mech by combining the power of the MC and one girl, but that basically reduces your party size to 2 because the girl you pick can’t do anything except move until the mech goes away.
If the MC reaches 0 hp it’s game over; if one of the girls reaches 0 hp you lose friendship value with them and they are out for that map.
The way the XP is done is weird. Enemies will often drop gems that give between 1 and 10 xp. 10 xp moves you up a level. But you have to get the gem before it disappears, and the last enemy you beat drops a gem but you don’t get it, even if it’s the boss and it gives you a 10 xp gem. Characters that did not join the battle get 5 xp for each one, which is not enough to keep them competitive.

For map design, there is some variety in the maps. Some of them are in the air like above (although it makes no sense because despite being in planes, everyone still retains their core attack types and ranges). Height and obstacles play a big role. There are a number of unique enemies with their own challenges.
The balance is not great. As I said above, the lack of any free battles means that if you didn’t focus all your XP on a few characters you are screwed. Moving up a level restores your HP — if it weren’t for this I think the game would be nearly impossible because all of the enemies in the game hit hard, from grunts to bosses. A lot of the grunts have their own powers and area attacks, and the bosses can sometimes hit from all the way across the screen. Losing even one character reduces your combat potential by 1/3 and so you can’t afford that at all unless you are almost done with the map.
The interface is fine, and I mentioned the extras above (the unlockable things from getting the friendship levels with the girls).
On the whole I wasn’t a big fan of the game. The harem part didn’t interest me, and the gameplay wasn’t good enough to make it interesting. The real problem, as I said several times above, is the severe limitations of the battle system.