Looks like AWS Kinesis Firehose is a way to ingest data (buffered together) to an object, is there a Kafka counterpart for this kind of functionality?
Yes, Kafka Connect, which is part of Apache Kafka.
You can use it with a variety of connectors, for streaming data in from a source (RDBMS, JMS, MQTT, CSV, etc etc) to a Kafka topic, and from a Kafka topic to a target (RDBMS, S3, BigQuery, HDFS, etc etc)
Kafka Connect in action:
Disclaimer: I work for Confluent.