Useful for fighting games like Mortal Kombat, Street Fighters, Tekken. This camera looks at the plane created by the line joining the two targets and vertical up

PlaneCamera.cs

using UnityEngine;

namespace Assets.Standard_Assets.Cameras.Scripts
{
    // Useful for fighting games like Mortal Kombat, Street Fighters, Tekken
    // This camera looks at the plane created by the line joining the two targets and vertical up
    public class PlaneCamera : MonoBehaviour
    {
        [SerializeField]
        private bool autoTarget = false;
        [SerializeField]
        private string target1Tag = "Player1";
        [SerializeField]
        private string target2Tag = "Player2";

        [SerializeField]
        private float minimumZoom = 3f;
        [SerializeField]
        private float maximumZoom = 7f;
        [SerializeField]
        private float zoomMultiplier = 1f;              // works well between 1f to 2f, use for increasing zoom effect
        [SerializeField]
        private float heightOffset = 1.5f;              // height from the ground

        [SerializeField]
        private bool smoothFollow = true;
        [SerializeField]
        private bool smoothLook = true;

        [SerializeField]
        private float lookSpeed = 0.03f;                // damping effect to prevent jittering, used when targets move left/right
        [SerializeField]
        private float followSpeed = 0.05f;              // damping effect to prevent jittering, used when targets move in in/out

        [SerializeField]
        private Transform target1 = null;
        [SerializeField]
        private Transform target2 = null;

        void FindTargets()
        {
            if (target1 == null)
                target1 = GameObject.FindGameObjectWithTag(target1Tag).transform;
            if (target2 == null)
                target2 = GameObject.FindGameObjectWithTag(target2Tag).transform;
        }

        // LateUpdate because we need to track objects which have moved in Update
        // Position the camera perpendicular to the line that connects the targets and Vertical up
        // Make the camera look at the mid point of the targets
        void LateUpdate()
        {
            if (autoTarget)
                FindTargets();
            if (target1 == null || target2 == null)
                return;     // nothing to do

            var midPoint = (target2.position + target1.position) / 2;
            var lineVector = target2.position - target1.position;       // this is the straight line that joins the targets

            var perToLine = Vector3.Cross(lineVector, Vector3.up);      // this is perpendicular to the above line
            perToLine = perToLine * zoomMultiplier;
            perToLine = perToLine.normalized * Mathf.Clamp(perToLine.magnitude, minimumZoom, maximumZoom);    // make sure it is in desired range

            var newPosition = midPoint - perToLine;
            newPosition.y += heightOffset;      // to prevent the camera being really close to ground

            // depending on whether smoothing is required, update the camera position and rotation
            transform.position = smoothFollow ? Vector3.Lerp(transform.position, newPosition, followSpeed) : newPosition;
            transform.rotation = smoothLook ? Quaternion.Lerp(transform.rotation, Quaternion.LookRotation(perToLine), lookSpeed) : Quaternion.LookRotation(midPoint);
        }
    }
}